Have they already made their reservations? This is one of their newest ships, so it is not listed on the disabled travel sites by what is accessible. It is also not listed as one of the specially designed ships for accessiblity on the Carnival website:
If they have not already reserved a special accessible room, I would be very leary of them being able to manage easily. Most rooms have a 4-6" lip going into the bathroom unless specially modified. At 16 he may also have near to an adult sized wheelchair, which may not fit through some cabin doors. Generally most public areas are fairly accessible on newer ships, but sometimes areas that are important to kids (like the arcade) may not be fully accessible. The pool on this ship is NOT accessible unless someone lifts him into the pool. How big is he? It would be best to call the Special services desk and have them discuss their special needs directly with a ship representative:
Carnival Special Needs staff at 1-800-438-6744, ext. 70025
While you are generally required to TRAVEL and stay with someone who can assist you when needed, you certainly do not need to be supervised by anyone on the ship. He should be able to get around the ship by himself. The only limitations are that some exterior doors (for example, leading to the Promanade deck or pool area) can be heavy, and on some ships have either a very short steep ramp or a 3-4 inch lip which would require assistance for most people to get over in a wheelchair. If he can safely direct this, often other passengers or crew will help. There is lots to do on any ship...arcade, computers, movies, lectures, Trivia, library, just relaxing and reading, watching for sea life, eating, etc. Of course he can take his Game Boy too! Often there are teen events and he should meet with the director for these programs at the beginning of the trip to see what can be adjusted to accomodate his participation. Also discuss this with the Special Needs staff.
Transferring to a car or taxi is easiest for shore trips. Don't expect any of the ship's shore excursions to be wheelchair accessible. Be sure he takes a manual wheelchair for this if he uses a power chair.
I hope this helps.