We celebrate with my dad's side some day before Christmas, whatever works. Then we go to my parent's and celebrate with immediate family on Christmas Eve. Finally, we celebrate with my mom's side on Christmas Day. "Celebrate" = potluck buffet style food (no real sit-down formal dinners), watch the little kiddies open their presents, and then just chat or play board games, share photos from recent trips, etc. With my immediate family, we sit in the basement with a fire going and watch whatever movies people have received as gifts.
Traditional foods = Chex Mix, banket (a pastry like thing, it's like a tube full of almond paste), and an assortment of jerkies made from various animals my uncles and dad have shot and butchered (this year was salmon, venison, and caribou).