Establishing relationship with Ex's New Girlfriend
Unless you have an explicit agreement in your parenting plan, he can have anyone he wants watch the kids during his parenting time. That's why a lot of people put this kind of language in their parenting plans (including me). Unfortunately, he does have the right to introduce his girlfriend to the kids on the day they meet, as well as have a parade of "serious girlfriends" if he wants to. The best thing now is to try to reach an agreement with him if you can. It sounds like he's willing to go along with you taking the right of first refusal, which is great. If you don't feel comfortable, you can continue to keep the kids when he's not free to be the caregiver during his time.
If I were you I would continue to let him know that I don't feel comfortable with how quickly he introduces the kids to his new love, even if it makes him uncomfortable. You don't have to fight about it, or try to force him to do it your way, but you can continue to be the voice that says it's best to be absolutely sure this is a long term relationship before introducing the kids. A few more girlfriends, and he might begin to see it your way, if you can calmly express your point of view to him. And of course, make it about the kids, never about you.
My agreement with my ex is that we get to meet anyone who will spend the night with the kids, before that happens. It doesn't give either of us the right to forbid them from spending the night, but it keeps a foot in the door so we are aware of who has night time access to our kids. This is a pretty simple and straightforward request, and it might be a good one for you to start with, with your ex. At least then you would get to feel the woman out yourself, instead of hearing about her from the kids.
Other than that, I think that if everyone is an adult, making the request to meet his girlfriend and get to know her, is not unreasonable at all. She is spending time with your small children, after all. I come from the perspective that having relationships come and go is not necessarily the end of the world for every kid. If you build up marriage as the end all of human relationships, then yes, it's going to be confusing and disappointing for them if their dad changes girlfriends twice a year. But if there is an extremely low level of drama, it could be as simple as, "she's doing other things now, so we don't really see her anymore". Not nearly as big of a deal. But I still think your perspective and concerns are very valid.
I don't think your feelings are unreasonable at all, but I think it is an aspect of co-parenting that may be the first of many places that you have to learn to live with disagreement. Like the previous response said, you no longer have complete control over who your kids get introduced to, who they spend time with, and what their role is in your child's life when they are with dad. Maybe if you start from a point of accepting his right to introduce his kids to other people, have other people watch them, etc, you can think of what you need to agree to to make it most comfortable for you and, more importantly, the kids.
As an example, perhaps rather than making it an issue of whether or not his girlfriends are "serious" before introducing them to the kids, you could talk about how you will talk to the kids about new people in their lives. If you think about it, kids meet new people all the time who are introduced to them as a parent's friend, and they might go through a period of seeing one or two of them quite a bit and then not seeing them too much at all... so see if you can get on the same page about how new people are introduced and how it is handled when that person isn't part of their life anymore... This would probably be a lot easier than trying to set some sort of threshold for when a relationship is serious enough to involve the kids.
As for having someone else watch the kids, again, talk about what your expectations are for someone who is going to watch the kids, as well as who is going to be allowed to pick the kids up from childcare. Don't think of it as his girlfriend, think of it as someone in general (a cousin, a babysitter, a neighbor, etc) who might care for your kids and what you would expect. For example, I wouldn't want someone picking my kids up from school who they'd never met before, and I wouldn't be comfortable with a babysitter who had no experience with kids. If you can establish some ground rules for vetting childcare arrangements in general, it might be easier to come to some agreement than if you tried to tell him when his girlfriend can be left in charge of the kids. You could also talk about whether you want to give one another the right of first refusal for childcare beyond a certain length of time (it's not really practical, and could be more difficult for the kids, if he has to give you first dibs when he wants to go to the grocery store,,, but in situations like the one he described, say beyond 3 or 4 hours, it might be nice for you to have the option of getting extra time with the kids.
And it is worth remembering through all this that whatever you ask of him you have to be willing to give in return. If you want to meet his girlfriend before she watches your kids, you are going to have to be willing to introduce your future babysitters to dad before they can watch the kids. If you want to be able to sign off on anyone he puts on the "okay to pick up" list at childcare, you have to be willing to let him veto someone that you want on the list if he disagrees. If you want to have right of first refusal for his childcare needs, you will have to offer him the same right next time you need childcare when the kids are with you.
Thanks ladies. Your perspectives are really helpful. We actually have right of first refusal in our parenting agreement, but we just divorced in March, so it hasn't had to have been used yet. So I'm guessing that just didn't even occur to him. It didn't occur to me until later. Aricha, I particularly like how you said to treat her and the situation as anybody who would be watching my children. I think the whole label of girlfriend and ex wife has an automatic association in my mind of tension (my own childhood issues) as a result making it more complicated than it needs to be. When honestly, after thinking about it, what I want to know about her is pretty basic and simple, such as her experience with children. I also recognize there probably are some control issues or lack thereof that I'm going to have to deal with and let go.
I only have time to skim through the prior responses, but I notice that you do have ROFR, but that you're also being advised to work on accepting that your ex will have new relationships and that you can't control them. This is true - and it takes some time and some work.
Even if you do get to the point of feeling more comfortable about your ex letting his GFs have semi-step-parent roles in your children's life (and more resigned to the fact that he evaluates "serious" relationships differently than you do), there is still a difference between a parent leaving the kids with someone close to them for a portion of their own parenting time; and a parent ceding all or most of their parenting time to someone else.
If, say, your ex had a meeting for a couple hours, during his all-day parenting time on Saturday, you might be within your rights to tell him to drop off the kids at your house on his way and pick them back up after the meeting. But that might not be exactly reasonable of you and such stickler-ism can lead to retaliation, where one parent uses ROFR to keep the kids from ever getting to visit grandparents or aunts, uncles and cousins, unless the corresponding parent stays there for the whole visit.
However, I don't see any reason why your ex's GF needs to have your kids for all of their waking hours, during one of your ex's parenting time stints. It seems pretty clear that it would be better for the kids to be with a parent, for that much time. You shouldn't let your ex make you feel unreasonable, for saying that. It's not about his GF or her skills with kids. It's about the fact that being parented is preferable to being cared for by someone else, for such a long period, when kids are so little.
I get along with my ex and his SO as well as anyone possibly could. And, on occasion, if he's doing a lot of traveling for work and misses some chunks of his parenting time, his wife will call and say she misses our twins and I'll drop them off to have dinner with her, or spend the night and do something fun with her the next day. After all, it's indisputable that they have an important, stable, lasting relationship with her. But even her baseline expectation is that, if my ex is going to be gone for his entire parenting time stint (or the part of it when our kids would be awake), then the kids will be with me. Arranging otherwise is the exception, not the rule.
Yeah, I am the stepparent, and love to spend time with my stepdaughter. My stepdaughter routinely spends time with me when her dad is not here... after school, a few hours on weekends, etc. My DH and his ex have ROFR written into their custody agreement as well, and she has no problem with a few hours here and there. But were DH to be gone for many hours, as you mentioned, it would be expected that DSD would go back to her mom's. There would be no question of it, and I don't think you should set a precedent of allowing your child to be away from both parents for long amounts of time like that. I don't think you EVER need to get comfortable with that situation, even if he ends up marrying this one!
Another way to look at schedule changes is what it feels like to the kids. It seems like you picking the kids up from school and dad getting them in the morning wouldn't feel that disruptive to the kids. If, however, dad was going to pick them up from school then he was going to drop them off with you an hour before bedtime and then pick them up again in the morning... then I would imagine having his GF care for them during that time would be less disruptive to their routine. Parenting is preferred to babysitting, but sometimes having someone else watch the kids is a better option for their sense of stability and predictability.
And in some cases, with parents (like my husband and his ex) who are fairly unable to agree to much of anything, ROFR could be disasterous. In our case, your parenting time was your parenting time according to the schedule, and if you weren't available you were responsible for finding appropriate childcare. You certainly were welcome to offer to give the other parent additional parenting time, but it wasn't your obligation. In some (high-conflict) cases it can be best to just stick to the schedule as it is written.
aricha, thats more like what my DP and his ex do. we all have quite good relationships with each other, but your parenting time is your parenting time, there is very little sending her back to the other parents for any reason. this was partially born of DPs ex telling the whole town that she had DSD 20 days out of the month instead of the exact 15 that she actually had. we are very careful to have DSDs parenting time split exactly. if she stays an extra night at her moms, we try to make it up by keeping her an extra night as well. i have been DSDs sole all day caregiver one day per week for some time now, but that was cleared with her mom first of course. in fact, DP made sure it was ok with his ex the first time i picked DSD up from daycare for 10 mins before he got home (we had not known each other very long though, maybe two months).
OP: would it work and would you be willing to adjust some time around, perhaps to have your ex pick up the kids on Thursday from preschool for an overnight, bring them to preschool Friday morning, and then get them again Saturday morning?
Independent of your knowing his GF (or knowing the person who is going to babysit if that were the case), given the ROFR, and in the interest of giving the kids as much time with their dad as possible, the one-time adjustment might be good. Yes it's an adjustment to the regular routine the kids know, but it at least emulates the parent time as much as possible, moreso than if they are with a babysitter/GF/whatever for most of the time anyway. If he was going to be gone from 7-11pm so he would be the person doing the pickup and at least be around for most of their waking evening, it might not be so bad, but he's probably not even going to get to see them at all Friday (I assume they don't stay up past 11pm!). Kindof a "what's the point?!"
If you do this, let him know it can't become the regular plan (to change things around in general, that is) unless you sit down and have a serious talk about it and come to a new agreement, of course. And if it is appropriate to switch around, he needs to learn to communicate with you that he'd like to switch things up. It could go both ways, as long as everyone is agreeable and the switching isn't abused (as in, the sense of routine becomes damaged or lost).
If his Friday night plans include "boozing," all of this is moot and he should just be glad with whatever reasonable alternative you offer, including "just pick them up Saturday morning." Not sure what kind of guy he is, hopefully this isn't the "problem." Of course, he's probably not going to tell you why he's busy, but you perhaps know him well enough to know if this is what's up.