This happens every bloody holiday.
DH and his ex never agree who is having (my) SD when during the holidays. DH won't ask her outright as he doesn't like arguments, his ex won't agree to anything unless asked outright (and not allowed to prevaricate)
So, again, we're at the first day of the holidays, and they are arguing about who should have SD when.
I like to do things during the holidays - visit friends, parents, and I think it's rude not to be able to tell them what day we'll see them and whether SD will be with us.
The DC and SD like to know what they're doing during the holidays - seeing friends/going on trips etc, and I can't organise this until I know when we have SD.
How hard is it - all they have to do is to agree who has SD first half of the holidays, and who has her the second half.
DH says I am being a nag - I just want to be able to plan to enjoy ourselves and have more than and 'dunno' answer when DC/SD ask me what we're going to do this holiday 
Rant over