Can you take one girl with you and one goes with him?

Tbh, the real issue isn't what to do on Sunday, but how you guys communicate & problem solve.

Personally, I think birthdays trump Christmas, previous agreements trump new ones & newly bereaved widowed grandparent trumps married aunt & uncle, but it's about what works best for the family. If you had similar values or ways of communicating, you may both be able to agree on what's best.

However, I don't think the issue here is about who's right or what's best but who wins.