I’ve been planning for 7 people at thanksgiving dinner. Now we might be as many as 14. All unconfirmed. What do I do???

If possible I would purchase extra pieces of the meal you can use again. For example, purchase turkey breasts which you can quickly cook per the new number of confirmed guests or freeze if they are no longer necessary to be used in a future meal. The same goes with things like sweet potatoes which can be quickly steamed in the microwave (super last minute) or stored in a cool, dry place until needed.

How rude of those extra 7 to not confirm until day-of!!! What about asking them to bring a dish or appetizer with them if they will be coming? You can always stretch stuffing with extra dried bread and chicken broth. I also like the idea of an extra cheese ball and/or squash soup to start dinner.

I'd probably make a nice squash soup to start things off, and help fill the bellies before the main stars hit the table. You could also add to the appetizers offered before the meal, to include things like a cheese board or ball, or a variety of cut veggies and dips. The decision to upsize the main event sides will depend on if the additional guests are adults or children, or some combo. Kids don't tend to go heavy on the veggie sides, adults will take a bit. Take this planning time to explore ways you can repurpose the leftovers in the days following the great feast, and what can be frozen to use another day. If you have a list of things you can make using a variety of things, the prospect of leftovers is a bit less overwhelming. You can make soup, bread, fish/seafood cakes with the mashed potatos. A great variety of finely chopped leftover veggies can be mixed with the potatos to make potato pancakes or waffles as well. Turkey bits can mix in with the green bean casserole, and used as a topper for toast, pasta, or potatos- including those pancakes I mentioned. Or you can send the guests off home with a gift of leftovers as well.

Hello! There are some easy sides on the food 52 website that might be helpful- https://food52.com/blog/23395-easy-sides-thanksgiving-recipes-few-ingredients
If that doesn't feel like the right route- my suggestion would be to round out the appetizer portion of the meal buy extra cheeses, breads, dips to help fill up before the main event.

If you have enough time between when they tell you they're coming, and when dinner is set to start, have on hand (but don't yet cook) extra ingredients for your easiest sides...stuffing, salad, etc.
When you hear how many are actually attending, make extra side dishes or amounts of already-planned sides.
For dessert and sauces (cranberry, gravy) I would make extra the day before.
These keep well and/or will likely be used up by family family or visitors around on the weekend after t-day.