For the
scooter question, the biggest issue is the weight the
ECV or wheelchair is designed for.
You want to have your total weight below the weight limit for that ECV/wheelchair (you, plus your clothes, plus anything you are carrying) .
I would suggest an ECV because it will give you more independence plus no one will need to push you.
For the wheelchair, the seat width is determined by weight. For
ECVs, if you are close or over the weight, the batteries will run out faster.
The larger scooters have bigger batteries to handle the larger load. So, you want to choose an ECV with a weight capacity higher than your actual weight.
I only saw one scooter type from Walker that you would be over the weight limit for.
The heavier duty ECVs also usually have a slightly different seat, but operate the same. The other decision is 3 or 4 wheels - the 4 wheeled ones are more stable and less likely to tip. The 3 wheeled ones are more maneuverable.
For the question about rides to avoid, there are 4 that I would recommend avoiding or seriously thinking of avoiding.
Big Thunder Mountain Railroad at MK is a runaway railroad car. It has steeply banked turns and just a lap bar for restraint. People often find their companion in the ride car banging into them as they change direction. If you wasn't to try it, I would suggest having your injured shoulder to the outside where you don't have to worry about the other person in the ride car.
Dinosaur at AK is a ride combining a simulator with a car that actually moves (and in dim light or darkness). The story of the ride involves going back to dinosaur times and includes a lot of sudden stops, sudden acceleration and changes of direction.
Primeval Whirl at AK combines the spinning of the teacups with a roller coaster. Some people find the ride bumps them up against the side of the ride vehicle or their neighbors.
Star Tours at the Studio is a large theater, simulator type attraction. It does bump around a lot in different directions, with frequent direction changes; since there are about 50 variation on the attraction, going once doesn't tell you much about the next time you ride.
There is a post on page 2 of the disABILITIES FAQs thread that lists all the attractions with warnings and a little more about them. That thread is near the top of this board or you can follow the link in my signature.
You can also look at
YouTube videos of many attractions, although some of them are dark and hard to see anything.
Between those things, you should have a pretty good idea and can use those things to discuss with your doctor.
