Great write up Rockhill,
The other thing worth considering may be getting a smaller unit she may be willing and better able to drive a 28' B+.
I can understand the trepidations to the surgery and the Dr's get nervous on them when your're over 70, but you may want to explore second opinios on it as well.
One last thought, If you still a sticks and bricks location as well as the MH, And have a couple of favorite places you visit seasonally, would a destination trailer in one of those locations be an option. It would allow you to go there whenever you wanted and you could travel in a passenger car. And you may even be able to offset the cost some by renting it out occasionally.