They would have Family Suites with several options:
1) Regular suites with regular bathtubs. You can request first floor or near an elevator, but that is just a request. If you request it, make sure they note it is for Medical Reasons; those requests are filled before other requests for the same thing.
2) Handicapped accessible with a regular tub with grab bars.
3) Fully wheelchair accessible with a roll in shower. These rooms have a shower that has no lip to step over. Someone with a rolling shower chair could roll the shower chair from the bathroom right into the shower. Those showers also have a built in bench that can be folded up for someone who doesn't want to sit and folded down for someone who needs to sit while they shower.
The rooms themselves would be the same size and general arrangement. The space would just be divided differently in the room with the roll in shower.
If you look in the disABILITIES FAQs thread, there is a section about resorts that shows an example of a roll in shower (the one shown is at Old Key West, but the idea is similar in all roll in showers). There is also a phone number for WDW Resort Special Reservations - they can help you with what you need.