If your renting a car, it shouldn't be to bad to use a gym at another resort.
Just drive over, and use it, of course there is a fee for resorts guests not staying at the gym's resort.
If you don't have a rental car, doing transfers to another hotel does take a lot of time. However, if your husband likes to workout, he'll figure something out.
Here's the resorts with gyms, from a pp.
Disney's Animal Kingdom Lodge -- Zahanati Fitness Center
Disney's BoardWalk -- Muscles & Bustles Health Club
Disney's Contemporary Resort -- Olympiad Fitness Center
Disney's Coronado Springs Resort -- LaVida Health Club
Disney's Grand Floridian Resort & Spa -- Disney's Grand Floridian Resort & Spa Health Club
Disney's Old Key West Resort -- R.E.S.T. Exercise Room
Disney's Polynesian Resort -- Disney's Grand Floridian Resort & Spa Health Club
Disney's Saratoga Springs Resort & Spa -- Disney's Saratoga Springs Resort & Spa Fitness Center
Wilderness Lodge and The Villas at Disney's Wilderness Lodge -- Sturdy Branches Fitness Center
Disney's Yacht & Beach Club and Beach Club Villas Resort -- Ship Shape Health Club
Connie