How do I deal with my family during Thanksgiving?

My parents are divorced, and for six years I went back and forth between houses. Last year I decided to live with my dad full time, because of some issues between my mother and me; even though my three younger sisters continued to switch back and forth. My mother accepted my decision, but repairing our relationship has been rough. I have been invited to my maternal grandparent's home for Thanksgiving; it is the first since I moved out. I am afraid that they will use this occasion as a way to voice their opinions. How do I deal with them respectfully? I really don't want further problems.