Hi Erin,
First, you have chosen a great resort because it is a very compact resort. The walk from the furthest room in the furthest building (building 1) is only 5 minutes to the main building (and I walk slow).
However, I would first call whomever you made the ressies with (Disney,
Travel agent) and make sure that it is noted on the reservation that your mother has difficuly walking and therefore you request a ground floor in a building close to the main area.
The problem with requesting a specific buidling is that, in your example, if you requested building 4, they may have a room that is actually further in building 4 than an available room in, say, building 5. So I would request a specific room type (like I mentioned above) and the reason why.
Then I would call the resort directly about two days before check-in date to make sure that they have that request.
When is your mom checking in? If she is checking in relatively early, she may be able to change locations at check-in if she is not happy. When she checks in, have them show her on the map where she is and ask to change if she doesn't like it. (I just got back from POP and even though I did all of the above, my request for a ground floor room near the parking lot was not fulfilled. I checked in around 4pm so there were plenty of rooms still available that I asked for a room meeting my needs.)
If she is checking in later on at night, call the resort directly again that morning and explain your request. Ask them to pre-assign a room for her. When we stayed at ASMovies last year, we checked in really late, around 10pm and, again, our request was not fulfilled, but there were no rooms that they could reassign us to. Most everyone was checked in already so we were stuck! I should have called that morning.
ENJOY!
