Wow, that's a real "challenge" for the cruiselines and you might have better luck getting more specific answers by dealing with the cruiseship's corporate office directly. I would consult with your grandfather's PCP on advice, options and what to request from the cruiseline in terms of preparedness & contingencies.

There are topics/discussions about various special needs over at the boards/forums at cruisecritic.com - goggle or search among the threads.

NCL has an "Access Desk" and you might want to contact them directly by phone, fax or email directly:
http://www.ncl.com/nclweb/cruiser/cm...ssibleCruising

I don't think the typical cruiseship cabins, including the "accessible" ones are designed to integrate (red tag outlets) backup power generator functions - in the unlikely event of a power failure (engine fire, etc.) A gas-powered generator will emit fumes and can be noisy while running, and must be properly setup to run with ventilation (out on the balcony) From my standpoint, there are many safety & risk management issues involved with having the equipment in a ship's cabin. ^

While you are exploring this - consider investing in AED and/or ask the cruiseline on whether the ship being sailed on carry an AED .... @:-)

Good luck & Alaska, yes, is a must see for anyone who ever wanted to cruise - for its scenic beauty.