Hello BMW and welcome to Cruise Chat.
I know they have wheelchairs available, but I am not certain on scooters (although I would think they would). You should contact your travel agent and have them find out the details for you. I am going to make a link of you post in the Disabled Travel Forum section too as there may be readers in that section that can answer your question too.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14, Freedom x 2 6/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013