Hi, Joanna!
I think a Family Suite at either
Disney's Art of Animation or
Disney's All-Star Music will be the perfect set-up for your party of 3. Each suite will have a bedroom with a queen bed and a living room with pull outs for up to 4 guests. This 2 room suite should be plenty of room for all spread out. In addition to the 2 rooms, each suite will have 2 full bathrooms and a kitchenette.
The suites at both resorts are very similar, but the Art of Animation is a newer resort, and a bit pricier. If you plan to spend a lot of time in the room and want a bit more upscale feel, go with the Art of Animation. For a more economical stay, All-Star Music will be perfect. These are both Value Resorts, so neither location will break the bank.
Visiting in early December is my favorite time to be at Walt Disney World. The crowds are manageable, the weather if comfortable, and Mickey Mouse has the park decked out for the holidays! If you schedule allows, plan to attend
Epcot's Candlelight Processional. It is a such a wonderful event that will really get you in the spirit of Christmas.
Wishing your family a magical vacation in Walt Disney World!
Cathy