This is just my personal opinion, but I think you need to leave the kids alone. You weren't a significant part of their lives while you two were dating--you said you (wisely) kept your distance. Why now try to be invoved with them when you need to remain NC with her for your own mental health?
It isn't that I don't feel badly for the kids but I just think you are powerless to help them, and might confuse them even more. If you want to save kids, volunteer to be a big brother or help with reading in schools. There are plenty of kids who need help that don't have your exagf as a mother.
Why is this even going through your head? I'm worried it is your AV. I don't say that in judgement; it feels like something I would do myself. Our AV gives us excuses disguised as altruism to contact our exes. Stay strong, Zen!