Would it make sense to talk to the kids about how long they want to be away and include them in the plan-making? This is about THEM, not her.
Lucky, what do you think?
Antlers, I think this should really be more about what you and your kids want to do with your time together.
The length of time sounds like it is out of the norm and maybe should be compromised some. You need to be honest with yourself about that. AND, I think you should make a mutual agreement about how long is ok for both of you. Then, you both feel respected.