I'm not 100% positive that it's fullyaccessible, but the studio I stayed in at Old Key West last year had two (queen) beds and a roll-in shower. I just don't remember if there were bars around the toilet, and frankly some of the stuff in the kitchenette was in the cabinets above the counter; anyway, check on the Disney Vacation Club boards for information about renting points from a member.
I'm not sure of all of the current places that would fit your needs. However I've stayed in 2 rooms at Port Orleans Riverside that had 2 double beds and a roll in shower.
Here is a nice thread discussing various rooms at the resorts:
Many of the resorts have now re-vamped their ADA rooms to now have two double beds and a roll in shower. You should probably just choose your preferred resort and expect to be accomodated with enough beds/space for your party size just the same as everyone else without a need for the roll in shower. ----Kathy