Hi Colleen, We were on the Celebration last year. Basiclly the ship is accessable. The rooms are not the best, but will do. The doors are wide enough for the chair ( I forgot to measure them.) The outside rooms are the same size as a regular (185 sq ft) 9.3 ft x 19.5. Of course out of that is the bath. The bathrooms are about 4 inches higher than the room, so they put a rampin the door. The rams are about 12in, so the rise is 1in for every 3in. The closets are across from the bath door (another words there is a little hallway), and the turning radius is minimal. Bath is usable, but not overly large. Beds are arranged along side walls instead of the L shapped arrangement shown in brocure pictures.
The 4 inside staterooms are better. There is no little hall way like the outside rooms. The Bathroom is still 4in higher with the ramp, but they are easier to access because of the open concept. Of course with these you have no window. It is kind of a trade off I guess.
The Public restrooms are NOT accessable. The doors are not wide, narrow tight turns and itsy-gitsy stalls. The Astoria lounge is marginally accessable if you can be creative. A few of the minor lounge/bars have steps, but most are open. Casino is OK. Pools, well not very unless you are creative.
Cozumel, ship docks at the pier. No accessable cabs, unless you use a portable chair. Hubby is in elctric one. Town has barriers unless you can navigate single steps and curbs 6-8 inch mostly. But mostly flat ground.
Playa del Carmen - you tender- NOT a good idea unless you are brave. Narrow walk plank and it moves A LOT. If you do get to Playa, x-caret is a lovely place, and is mostly level with a few curbs or single steps 6-8in.
We will be on the Rhapsody this Dec, and will take a folding manual chair to let us navigate in Cozumel.
All in all. The ship is usable, and Cozumel is a lovely island. Just get adventurous and go ahead.