You can't come on to strong. He can't see any doubt in your mind, or he will attack it. Heck, he'll probably attack anyway, so don't give him anything to aim at.
I might even leave out "for now". He could grab onto that, and try to get you into a dicussion of the future. I don't think this is a good time for that. Sure, it needs to be talked about, but after things are stabilized.
As far as "custody" or "co-parenting", at your daughter's age it isn't much more of an issue than it is for your son. No matter what is ordered, she is going to do what she wants. I don't think I'd say much about it unless D wants to talk about it. The most I might say is that "we would like you to be comfortable spending time with either of us."
No second-guessing or doubts, Bunny! You are doing the right thing.
