I'm confused about what the issue is here. What kind of "activities" does the mom want planned in advance? Are you talking about her wanting to know that they'll be playing Scrabble in your DD's bedroom between 3 and 4, or that you'll all be going to the local museum, or what? To my mind the former is unreasonable but the latter isn't - I'd feel some anxiety at not knowing where my DS was going to be while not under my supervision. (I mean, I deal with this if there's a good reason why I might not know in advance, and I dare say that will happen more often as he gets older, but still, if he were spending time with someone I didn't know well, I can imagine probing if the possibility of going out were mentioned.) If going out is the issue, I think I'd just get the girls to make a list of all the places they might want to go, and tell the mom that they might or might not go to one of those places. If you don't already swap mobile phone numbers as a matter of routine, that might help reassure her too.
