Brook, Let it Go. He needs to be the parent on this trip, no matter how big a fail he may be. Let him handle it. It's not your job to make this trip a success, it's his.
The girls hopefully, will let him know if there's something they can't live without. Maybe just tell them that it's important to ask for what they need/want to take and discuss it with their dad. In order to survive their father's character defects, they will NEED to learn early to speak up in order to get their needs met. Let them.
I don't think you should be the in-between...anymore than you have to.
Let God handle this one. :-)
"You know, it's times like these when I realize what a superhero I am." Tony Stark/Iron Man
“Focus on what you can do, then do it with all your heart.” Lois Wilson
