NTA at all.

One night isn’t going to kill her and the kids can call her when it’s convenient to them as well. Phones work both way.

Also, just have him text her that you will be heading out for the evening and will have limited phone time due to activities. For one night. If she can’t understand that - serious issues with that woman. One night of no contact bc of a vacation isn’t denying her access to her children.

Lastly, It isn’t your job to “walk on eggshells” to not create “waves.” Forget that noise. She has zero issues creating waves in your family, perhaps it’s time to actually start setting some strong boundaries for your family. It’s total BS he does not want to create waves with her but has zero problems drowning you in a tsunami of waves to avoid waves with her. Unreal.