Good luck with the visit- it is great that you are planning ahead. In school (full disclosure, I'm a psychologist ) we always talked about how "activity is the antidote to anxiety" (for example, if we found ourselves being much more "active" in a session with a patient, than we might want to ask ourselves if something was making us anxious). Anyway, I know that when I'm anxious DOING something makes a huge difference (and keeps me from emotional eating, which is my downfall). So, even though you can't stop by a mall to browse, I'm sure there are other things you can do at your parents house to stay busy and to take your mind off a situation that has triggered you. Without knowing any more about what you have gone through with your parents or about your kids, I thought of these off the top of my head:
-watch a TV show or movie with your kids- something that you actuall LIKE and that will be engaging
-along the lines of taking a walk, any sort of physical activity.. wrestling with the kids, start up a game of soccer, etc.
- maybe have a list of a few other friends to call besides DH (in case he isn't able to answer, or just in case you find yourself wanting to call for support a lot and want to spread it out :)
Another thought I had was planning ahead for ways to avoid triggers. I know you said that you could avoid engaging with your mom.. I have personally found that hard to do! Although it has gotten WAY better with practice. I also found that having an actual PLAN for how to communicate with her helps..even if it sounds stupid... for example, I play a little game with myself to see how few words I can use to respond to her without actually seeming to be rude or be visibly acting weird. I also tell myself to agree with her 3x as often as disagree, and somehow even trying to keep count during a conversation keeps me distracted and busy. You could plan a few longer-range tasks to do around the house while you are there that would keep you busy and also give you something to do if you needed time away from her. I don't know what their place is like, but maybe you could offer to dig them a flower bed and do some planting, or maybe there is a basement that could be re-organized or a room that could use some painting. Just brainstorming. Double whammy of looking like a great daughter for offering to do something for them, and having a task that keeps you busy and focused. Will you be able to get away with the kids at all, or are you stuck in the house the whole time? maybe you guys can get a marathon board game competition going, or set up a week-long series of funny family olympics, or plan to try out a new recipe every day.... anything to give structure and to keep you guys busy and not engaged with mom.
last thought- could you plan ahead of time to call a friend every night (or after noon or morning or all of the above) for scheduled check-ins and pep talks? even just 5 mintues may help keep you focused and present. And it will avoid the situation of only having support from people who love you when you are already upset... maybe the few minutes of attention from someone who is in your corner can help head off problems at the pass.