We celebrate on Christmas Eve. Traditionally, everyone would wait up, have a late dinner, go to Midnight Mass and, then (after midnight, so technically Christmas Day), exchange gifts. My atheist/agnostic family would skip Midnight Mass and the kids were sent up to get some sleep/nap at around 8pm and then be called down for Christmas Diner at 10pm. Then gifts would be opened at midnight.
There would be all sorts of appetizers and little snacks out for the adults, throughout the evening. The kids would get a light super before going to bed. Then, at 10pm, we would have fondue for dinner, since it is a slow meal, perfect for chatting and waiting for midnight. Dessert would be Christmas desserts: an assortment of dried fruits, sugared fruits and nuts, panetone (a sweet, fluffy bread filled with fruits and nuts), etc, followed by liqueurs and coffee.