First, I'm sorry to read about the accident. I'm glad you are ok, I hope it all works out in the end.
The crap with your H is tricky, isn't it! It's not surprising that your D's are excited by the change. Here's what I think. For now, and for a few years, he will be able to "fool" them. (At least the younger one, the older, maybe not.) But in the end, they are going to see who and what he is on their own. IT would be really bad for you to do anything to try to help that along. For now they need to love and respect him, even if he doesn't deserve it.
So, I don't think that you have to act excited for him, but I think it would be best if you didn't show your hurt, either. One reason being the kids. The other being that any negativity he feels from you is going to justify his actions, in his mind. So, I don't think you need to throw a party, but try to stay calm about it, I think.
