The Grandstand also has two other buildings that are not close to the Carriage House. Why not stay in the Springs? The furthest buildings are just across the street from the High Rocks Pool. Check out this map - http://www.wdwinfo.com/resortmaps/Saratoga.htm
We are driving home from SSR today and stayed in Congress Park in Building 3 and the walk only took five minutes to walk to the Carriage House from there. The advantage of the Grandstand is it is the first stop when you are going to the parks and coming from the parks.
We've stayed on one of those two buildings and they really aren't that much further from the Carriage House than the other buildings in the Grandstand.
We've stayed in the Springs, Congress Park, and Carousel. I would definitely stay in the first two again, but not Carousel. It's too far from a pool and from the bus stop.
I would request the Grandstand. Short walk to the Carriage House and main pool, there is a nice small pool at the Grandstand with a small splash pad area. The best part about the Grandstand is it is the first bus pickup and drop off.