We were on Mariner of the Seas last month. I was using a 'rollator' since I just had knee surgery. One of the Windjammer staff always hustled right over and carried my plate and silverware to a table then brought me my drink after parking my rollator out of the way. I couldn't have been happier.
If something happens while you are in port, such as being hit by a car or missing the ship, you are going to wish you had your passport with you. It doesn't do you any good in your safe on board the ship.