While you'll want a few pictures with everyone in one big group, it's often easier to get good pictures if you take smaller group shots--like just the spouses or the siblings--or even single-person portraits.
You can certainly position your subjects in front of traditional holiday backgrounds; but this year, try to stage some portraits in more organic, natural settings so that they look a bit more candid. Take pictures of people carving the turkey, lighting the candles, washing the dishes, setting the table, and refilling the candy dish. Such images can be more meaningful in the long run, because they strongly connect the people with the event.
If you go this route, though, be careful with the backgrounds. It's easy to end up shooting pictures in front of backgrounds so cluttered that they're a distraction. For the dish-washing pictures, for instance, you may need to move the huge stack of dirty dishes out of the way.
And though your digital camera tries hard, its built-in flash is designed to throw light only about 8 or 10 feet. What can you do? Avoid taking indoor shots of groups so large that you must stand halfway across the room. If you're photographing more than a handful of people, take it outdoors--and shoot in the shade, where direct sunlight won't shine right into the scene.