If you have a rental car you should keep the Disney Institute in mind. They have the best excercise facilities in WDW and a great spa with a wide range of treatments. My wife an I get a length of stay excercise pass for about $35.00 which gives us use of the facilities for our entire stay at any WDW reosrt. They have a huge indoor basketball court as well which i use to supplement my cardio workout. The locker rooms are the finest and best maintained on property. And after you've pampered yourself you can dine at one of the best restaurants on property, a rather well kept secret. Seasons is a first rate restaurant and well worth the trip even if just to dine. I would suggest that you drive over there to look around and then decide for yourselves. They will allow you to walk through the locker and fitness areas. Perhaps plan a meal at Seasons while you're at it to make it memorable, followed by a nice leasurely walk through the Downtown Disney area, which is right next door. For us that would be the perfect down day.
