definitely rent off-site, you'll have the
scooter back at the resort. This way its easy to move around resort, and don't have to worry about the long way to the bus stops, and resort, and bus stops and the entrance where the scooter rental is.
Don't worry about your husband. You will be happier if you are pain free, and you will be less grumpy. If your having problems at home, things won't get easier at the parks, with tons of walking, standing.
Just follow the signs, and ask the CMs at the beginning of the ride, anything special you need to know. MK has a few exceptions, since its so old, other parks more straight forward hit the main entrance, and follow the line.
Have a great trip motering around. Practice back at the resort. Things to practice, parallel parking, backing up, turning corners.
Don't forget there is a knob which controls the speed of the scooter. Turtle (slow) and rabbit (fast). So, when your in clear area, not people around, you can move faster more of rabbit pace. When your in a store, in a line that is really pokey slow, turn it to turtle. When parking on the bus, or in an attraction space, turn it to slow. Something else to remember. When you push the handle, if you want to go slow, don't depress the handle all the way. When your trying to make a tight turn, only slightly press the lever, to turn in a small space.