Call your t/a - there are accessible rooms on this ship - there may still be some available for your sailing. You will have to complete a medical form to show why you need this room. The accessible rooms are in several categories and are the same cost as a regular room.
Another point to ponder is this: You MUST inform RCI if you will be using as wheelchair on board the ship, as they have to know how many disabled passengers they are carrying at all times.
It's not an RCI rule, I believe it is maritime law that dictates this.
So whether or not you upgrade, let RCI know anyway.