For us we are ALWAYS away as we never have Christmas at Home and at at one of the Centre Parcs on the big day so we tend to get up quite late (as you would on a holiday!), open presents, head out to lunch around 2pm and then go for a big swim to burn off the calories from the dinner and then sort of veg out for the rest of the evening.
As a kid, I remember Christmas stating around 6am when I work up!! Is it a long day for those of you with young kids, I tend to find the whole day quite a relaxing affair really compared to the run up and endless buying of presents.