I would set out a few different kinds of bread, good deli sliced meats, cheeses, and sandwich fixings along with some paper plates, fruit, chips and Christmas cookies and let everyone help themselves.
I find that even though it's typical lunch fare, people enjoy having more choices than they would normally have in their fridge. Better breads, more stuff available to put on it, etc. If it weren't the holidays I'd probably make a salad, like brocolli salad, bean and corn salad or something like that to have out with the sandwich stuff, but with so much food around at the holidays I'd stick to really simple!