Christmas eve has no tradition, really. It depends on where we are, my wife's parents and mine lived about 5 hours apart, so as newlyweds we split the holidays. Which was no big deal to either of us. Once children came on the scene, we hunkered down and had Christmas Eve and Christmas Day at our house, in-laws were welcome to come if they wanted to. My folks usually did, hers usually didn't. But we went both places either before or after for the Christmas thing. Her folks were more traditional in the food department.
Now you want to talk about set in stone, don't even bother to bring it up is Christmas morning. Her grandmother used to fix a big breakfast and her children kind of wandered in and out in their way to and from wherever. So, my wife has made that our tradition.
Country ham, eggs, cheese biscuits, grits, gravy, and so forth. But the piece de resistance is what we called sop, that came from my side. Others called it chocolate gravy. A thick, sweet, sticky, ooey gooey chocolate syrup like thing cooked in a pot on the stove that you put on your biscuits, dipped your ham in (the sweet and salty is something else). My sweet wife will cut you if you mess with her Christmas morning breakfast.
