It's hard to say without knowing more about the situation (and the community, I guess). I don't have kids yet, so that part I can't speak to, but in general I think the easiest thing to do is to skip the labels and just say you're interested in dating women. Who you've been with in the past is an important part of your story, and obviously you'll want to tell partners about that past (and possibly that you'd be open to dating men again in the future, if that's the case and it seems relevant). But if for now what you are looking for is a woman, that should be the main thing.
Bi gets a tough rap, and I think it's mostly either ignorance or just the fact that it's a good scapegoat--since most people won't own up to it (preferring to go with whatever their dating status is instead--oh! I've got a girlfriend, I'm a lesbian. Now I have a boyfriend, so I'm straight). There is also some contention over whether there are two genders, since so many people feel that they fall somewhere on a spectrum. I understand all of that, but it sounds like this is less about having a debate on LGBTQ terminology and more about getting a date, so I don't think it should matter much.
Same thing goes for the poly stuff--if you're interested in having an open relationship or many relationships, I think you should just be up front about that when you meet potential partners. Some people won't be up for it (I know I can't do more than one at a time) but others will be and then you can negotiate the terms in whatever way suits you both.
Where to meet them? Are there any queer-friendly churches of your personal persuasion nearby? Any queer meetup groups or volunteer organizations? Any family groups? And if not, here's always the internet... Good luck!