If you plan to spend Christmas with your extended family, this tend to get complicated. Now there are contributing factors here, maybe only one side of your family really gets together or maybe all of your family is out of town. Whatever the dynamics are I strongly suggest you talk ahead of time and make a plan so that when the holidays come around your ready to go and your family knows what to expect.
In my family most of my husbands extended family live within 45 min from us, but my family all live about 3 1/2 hours away. Before we even got married the holiday season was discussed and for us since our familys were so far apart it worked out pretty well one year its Thanksgiving with his famiy and Christmas with mine and the next year we flip.
Now if you have family all in town, or maybe you only celebrate with your family, this obviously changes things. Personaly I think it would be harder and beocome overwhelmed if your entire family was in town. I would want to see them all on Christmas day and that just might not be possiable. Maybe you can, maybe you can do one family in the morning and another in the evening.
Whatever you do just make sure it works for you and that your in agreement.