I would go with the Contemporary and if you can afford it I would go with a Tower room, no matter if it's the Magic Kingdom or Bay Lake View. Since you stated your MIL will be in a wheelchair staying in one of their Tower rooms would be great because everything like you're room, restaurants, stores and lobby and lobby are located all in one location. Plus on the 4th floor there is a special elevator just for people in wheelchairs that goes to the Monorail station. Besides that all the room rates at the Contemporary are the least expensive when you compare the rates for the Polynesian and Grand Floridian.