Don't get into it... Just tell him "we are going" and ignore him.
Say it once, firmly. Tell your kids ASAP so its locked in there. Tell everyone relevant. If you have someone coming by to watch the house while you're gone arrange that too.
Put money on the hotel too... everything... put it ALL IN.
He's giong to be like a kid going to the dentist... Don't argue, just say "you're going"
