I've done this before for family. I sure hope some of your guests are bringing food too. Have them bring desserts and appetizers - then you can concentrate on the dinner.
Spiral sliced ham is a great idea. You could also throw a turkey breast in the oven if there are people who don't like ham. Parker house rolls are good too - some people and kids like to make little sandwiches with them. I'd do green beans instead of broccoli - I've discovered that lots of people don't like broccoli. You could also put out a big bowl of greens for salad. If you want a little different salad, these recipes are good:
http://www.epicurious.com/recipes/food/views/Mixed-Green-Salad-with-Oranges-Dried-Cranberries-and-Pecans-15661
http://www.epicurious.com/recipes/food/views/Southwestern-Christmas-Salad-2818
http://www.epicurious.com/recipes/food/views/Arugula-Salad-With-Oranges-Pomegranate-Seeds-and-Goat-Cheese-107262
Fruit salad or platter is a good idea too - some kids don't eat vegies but will gobble up the fruit and it adds color to the buffet table.
I make this sweet potato recipe for both Thanksgiving and Christmas, but my dad's from the South and loves his sweet potatoes
http://www.epicurious.com/recipes/food/views/Whipped-Sweet-Potatoes-with-Brown-Sugar-Pecan-Topping-4668
Drink ideas? Wine/beer for the grownups and sparkling cider for the kids?
Good luck and Merry Christmas!