What would you do in this situation?

I have two family members passing through this weekend, from out of state.

The last time she visited one of the in-law’s caused a huge fight, revolving around her visit.

This time she asked me not to tell them she is here and we’ll have a small dinner. And she is bringing her teen son.

The issue is that I am very close to the other parties and am afraid if they find out, we will have issues between we locals.

What would you do?