Look on the deckplans and make sure that the room is marked as accessible. If it is then it will be fully wheelchair adapted - esp in the bathroom. You should have been sent a medical questionnaire to complete where you detail the size of the wheelchair - if you haven't then chase the T/A for this.
WE have seen very many people with wheelchairs on the RC ships and they seem to be extremely well catered for. I think the only frustration I have witnessed is it can take a while for a lift with enough space on it to arrive so leave plenty of time if you need to be somewhere on the ship.