The DTD bus stop is near SSR. I can't really remember how the walkway comes out though. Someone here will know, I'm sure. If you are going to a dinner ressie during park hours, you can always take a monorail back to MK and take a bus from there. If the parks are closed by that time, then I would likely be inclined to drive. Your problem will be getting all 12 there and back that way. The bus to DTD can be a long wait at night. Not sure why that is, but it seems to be true from a lot of the resorts. We almost always rent a car specifically for getting back and forth to the airport, grocery shopping and for dinner ressies at the other resorts after park closing.
Another tactic would be fro part of the group to drive and part to take Disney transportation. From the Poly, you would have two options when using parks as a go between...go to MK on the monorail and bus from there or go to Epcot on the monorail and bus from there (since that one is always open later). The other option other than driving in two shifts is that DTD bus. My experience is that you could likely make TWO trips with the car in less time than the whole group could get back on the bus through DTD.