Just a quick few things. It's not your place to play the mediator between him and the kids at this point. I wouldn't talk badly about him in front of them, but to reach out to him for coffee to talk about the kids is only a temporary fix to the withdraw you're feeling.
It sounds like you are attempting to convince yourself if you are at least friends that you'll settle for that, which I believe isn't your goal.
My guess is he's asking about you to the kids as a bridge to his relationship with them. That's all it is.
