I would have them contact special services: 
Disney Cruise Line Special Services  Phone: (407) 566-3602  Fax: (407) 566-3760  TTY: (407) 566-7455  Email: 
SpecialServices@disneycruise.com
If they are in an accessible stateroom, I would assume there is room for an 
ECV.  If it is a regular stateroom there is definitely not enough room.  I thought there was a charging/parking area for 
ECVs by Midship elevators...just not sure which floor...maybe the 5th on the Magic?