question about "permission"

XMrsV2005

XH and I share joint custody -- temporarily. We have joint decision making and 50/50 parenting time.

He has been sick since thanksgiving and hasn't really had the kids much. I have tried offering extra parenting time for him since he hasn't seen them, but he hasn't taken me up on it. Not sure if that's relevant.

This weekend my extended family is celebrating Christmas, approx 2 hours away. Unfortunately, I am going to have to work and will not be able to go. It is my weekend scheduled to be with the kids, so I'm not asking for a change in the schedule. All I want is for my mom to be able to take the kids to visit my grandma and aunts/uncles/cousins/etc.

Do I need XH's "permission" to allow them to travel with my mom? The kids are 4 and 22 mos old. 

I am going to email my attorney but I don't know if she'll be able to respond immediately.