Thanks very much for your responses, longrun and busting. The kids are doing okay. They seem to want to talk about the logistical side of things: whether they are going to have to move, where will I be moving, will we go on vacation together, that kind of thing.
It also turns out that W discussed b-day parties with the kids, and told them that "of course", I would come to family functions and parties and things.
I told her that, for my own protection, I can't be "friends" with her, although I would do my best to co-parent with her. Still, I know I can't be a part of her family's get-togethers, because I need to move on with my own life. I mentioned it to the kids, and they seemed to understand. I'm going to keep talking and, more importantly, listening, and I'm hopeful that we can work out these details.
M41 W42 M 12 T 15 S10, D9, twin Ds 3 1/2 BD 1/2/2013 Living as roommates Working on D agreement w. mediator 5/13