Great question... thinking about this as well.
We were definitely thinking Artist Point at WL. I think the atmosphere will make it magical. Only problem is that it's hard to see the fireworks, especially if the park's crowded and when can't get in due to full capacity.
In terms of inside the parks, I was thinking of playing it safe with Le Cellier in Epcot. I know Liberty Tree Tavern usually does holiday meals.
Sorry this isn't much help... we haven't been back for Christmas Day/Eve in a long, long time. Anxious to see what other posters suggest...