Maybe my experience (and mistakes) can help a bit. My husband announced mid-August that he was leaving.
My 24-year-old son lives in Philly (we live in the midwest) and felt guilty, that if he had been home, he might have been able to help (he couldn't have, but it's a normal reaction). He also worried about me, since Dad was supposed to take care of all of us and he isn't. He has seen a counselor in Philly and is doing much better, since he can see that I am doing much better.
Second son, 23, out of college, living at home while looking for a job. Became my AH's frat boy, always ready and available to go out drinking. Not good for my son....but he just got a job out of town and leaves Monday, so he's escaping!
Daughter, 20 won't speak to her dad. She told him earlier in the summer that if he left, she was done with him. She and I are very close, and I made the mistake of telling her too much, treating her as a friend. She has her own "daughter" issues to deal with and shouldn't have to hear about the "wife" side, so I share those things with adult women. AH continues to try to force contact with her. She is in counseling and is doing well learning how to set boundaries.
Youngest just left for college, AH has been trashing me to her for months. Instead of fighting back, I've decided to just continue to be Mom and trust her, trust God, trust that the truth will win out. So far so good.
Teenagers in general are not big talkers (with parents!) so maybe build your relationship on what's going on in their lives, and less about how you're feeling. They really are very selfish, right? And go to friends, SR, counselor for help dealing with your feelings. Also some other resources for mid-life divorcing women.
Good luck....sounds like you're a great Mom and your kids are old enough to see what's going on. Trust them, trust yourself. Just be there, which your AH is not. Let us hear how it's going.