Hi, we just got back from a southern Caribbean on the Magic, and have cruised twice before (Magic and Fantasy) with Mom using a wheelchair. If your person can safely drive a power
scooter, I would strongly suggest it. while you can get a wheelchair up and down the aisles of the ship to the cabins (we have done this, and a scooter allows you to deal with the carry-on luggage)), a scooter is narrower and much easier. (our last trip). It gives them greater freedom of movement and You will also benefit by not having to push the person around.
at both the world and on the ship, Mom would drive the scooter into the restaurant, transfer to a chair and they would park the scooter elsewhere. Also since it appears you will be doing a three or four day on the dream, you will want it for castaway key (there are beach wheelchairs once you get to either the family or adult beach). Nassau wasn't really handicap friendly if I remember correctly, and a lot of people stay on board that day as well.
One of your big challenges will be the gangways at the ports, which will depend on the tides (they can be rather steep).
A handicap cabin will be much easier to negotiate - bigger, and the bathroom setup is much friendlier. Also while I know you think a table for two is better, you might just find that you would enjoy the company of other guests.
John