Me and dd have planned a girly trip together for years which my mother kind of hijacked and said she would love to come.
Which was fine when I thought ex h would have the other dcs (separate holiday planned for them so they're not missing out.
However he won't have them and that's the only week we can logistically go 
AIBU to think my mum might step down and offer to babysit whilst I go with dd?
She's not hard done by, she took 3 holidays last year, one was a business class RTW trip!!
The fact remains that if she doesn't then no one goes! And she is welcome to come on the proper family holiday