I believe that bldgs that are 3 or more floors have to have elevators. Since the mansions are 3 floors, they all have elevators. But, there aren't several banks of elevators per bldg. You will find possible two elevators, in the center of each bldg. Then, you will have to make your way to your room.
The AB bldgs have no elevators. If there is any kind of 'stair' issue, then you are best off mentioning it when you make your reservation.
According to the ADA, buildings with more than 2 floors have to have elevators (if the building was completed after the date of the requirement in 1993). I think AB buildings only have 2 floors. I know they don't have elevators.
The elevators in the mansions are a little hard to find the first time. I think that area is also called Magnolia Bend. I'd suggest you ask the CM where they are in reference to your room before you leave the check in area. It took us a while to find them the first time we were looking.