Don't worry about the lifeboat drill, just let someone at the purser's desk know that you would need assistance in the MOST UNLIKELY situation where anyone would have to abandon ship. A wheelchair sounds like a good idea, because the length of the ship is VERY long and no need for you to exhaust yourself throughout the cruise.
Another suggestion that my sister & I learned when we took my mother on a cruise who was in a wheelchair, when waiting for an elevator during busy times, push both the UP and DOWN button and take whichever way it goes! It always has to return, and you won't be waiting forever for an elevator with plenty of room!
Have a great time!!
8/92 Mex. Riv. Commodore
9/98, 9/00, 9/02 & 7/04 Caribbean - Paradise
10/00, 08/05 Pac. Wtrs. Holiday, Monarch
04/06 Hawaii - Celebrity Summit
09/07 Alaska - Celebrity Summit
07/09 Western Caribbean RCCL Liberty of the Seas