If you have 4 guests in your immediate party with the dining plan, themax credits you can use at a TS are 4. QS seems a little more gray but unlikely you could ring up more than 4 at once.
You could make sure the resort guests order the more expensive menu items, switching the plates if necessary. You might save a few dollars. 2 desserts might be enough for 4 guests.
Nothing you can do for fixed price restaurants.