Your hospitality is inspiring, as well as your willingness to accommodate so many different diets/appetites, etc.
A turkey breast is a great idea.
Then, instead of mashed potatoes, how about baked potatoes? If you don't buy a bag of potatoes but select the individual ones in the grocery store, you can choose smaller potatoes. Serve with butter, maybe a lactose free butter substitute, and sour cream (on the side, so people can dress up their own potatoes), and it will satisfy the potato lovers.
You can also bake sweet potatoes. Provide some interesting toppings like crumbled cooked bacon, mini marshmallows, butter, brown sugar, chopped nuts, and let people choose their own toppings.
All those potato toppings can be prepared in advance. Buy a few small plastic containers with lids at a dollar store or grocery store and fill them with potato/sweet potato toppings a few days before Thanksgiving.
Instead of green bean casserole, you could make a colorful salad. Use baby spinach, mandarin orange segments (from a jar), Craisins (those sweetened dry cranberries), chopped pistachios or walnuts or pecans, and nice crisp croutons. Serve with a berry vinaigrette salad dressing (raspberry, etc - there are some good choices of bottled dressings).
Those Pepperidge Farm bags of stuffing bread cubes are pretty simple, and already seasoned. Just get a good box of chicken stock (like Kitchen Basics brand) and you can make just a small pan of stuffing using only as much of the stuffing bread as you wish.
Even if you're usually a stickler for homemade/from scratch stuff, take advantage of a few shortcuts, like canned cranberry sauce, a good quality jarred gravy, dinner rolls from the bakery department at the grocery store, and a pie ordered in advance.
I think when serving a smaller group, the smells and colors are important. With a menu like this, you'll have the potatoes, the bright colors, and the smell of turkey and pie, and it's all pretty easy.
