GENERAL ECV ADVICE:
One big piece of advice is be sure to rent a 3 wheeled scooter instead of the 4. The 3 wheeled ones are so much easier to maneuver and allow for a tighter turn radius that really comes into play when loading onto the buses. But it will help in ride queues and when trying to back into or out of elevators & other tight spots as well.
If you really get in a bind, keep in mind that there is a switch on the back of the scooter that makes it so you can manually manipulate it. If you ask, most bus drivers are more than happy to let you get off the scooter & use this feature to park your scooter for you. This is how CMs are able to move your scooter without the key while you're on the rides. If by chance you get on your scooter & it doesn't work, check to make sure the release isn't still engaged. This happened to me my first time after the Jungle Cruise and I thought my scooter was broken.
Be sure to plug your ECV in every night to charge while you sleep. I have found that the charge indicators will show as full until they're not. No gradual notice. Also, take your charge cord with you. In a pinch I've charged my scooter in the parks. This isn't usually necessary but better safe than sorry I say.
Those vinyl seats can get hot and sticky. I always bring a bright, unusual beach towel to put on my seat. This also helps you find your scooter in the "sea of scooters" that you can sometimes find after your ride. If you're crafty you can fashion a seat cover out of a beach towel that fits over the back of the scooter and onto the seat. My mom made me one years ago that I used until it literally fell apart. It was super easy to use & didn't fall off when getting on/off the scooter. I need to make another one if I can figure out a sewing machine. Lol
BUSES:
One note of caution, it used to be the case that they always loaded scooters first. When I was there in November, that had changed in some locations. If this happens, you'll need to be extra careful when loading.
Some people refused to budge an inch, even though I was trying to warn them that pulling their feet in was for their safety. More than once the driver had to intervene & ask people who had their legs fully extended into the aisle to please move their feet back. This was the exception of course. But be aware some people have a prejudice about scooters. Most people are just unaware of the dynamics of riding & maneuvering one.
This change was due to a change at some parks where the scooters are to get in the regular line & are pulled out to load when they get to that section of the queue. This is I believe an attempt to appease people who complained that scooters were given preferential treatment in being loaded first.
I can tell you that many able bodied people commented that this seemed like a bad idea and that they were actually going to contact guest services to say as much. A little dialogue with people really opened their eyes to the challenges we wheelchair/ECV people face.
RIDES:
I, too, have back problems (just had a lumbar Laminectomy on Jan 9 & will have a cervical fusion March 4). While most rides with those warnings do pose a significant issue (Safari, Dinosaur, BTMRR, etc) you will see warning signs on the tamer rides (IASM, POC) as well. I think due to the possibility of the boats coming into contact with each other at times? Watching
YouTube videos as a PP suggested is a good idea. You'll get a good idea of the amount of jerking around that occurs.
If there is a moving walkway on the ride (HM, SE, etc) and you have balance issues, just ask & they'll slow or stop the walkway for you to load & unload.
Some ride queues are dark. If low vision becomes an issue for you, turn on your front light on your ECV for some added help. Also, those displays on the top of the tiller can be blindingly bright & make it hard to see what's in front of you. I used my key fob (a piece of thick paper will do) to block it out so I could see better in the dark.
RESTAURANTS/SHOPS:
If you are able, it's usually a good idea to park your ECV outside & go into shops & restaurants on foot. It gives your bum a break from the scooter & allows you to browse shops much easier & navigate restaurant aisles easier. These areas get congested and can be difficult to navigate or extricate yourself from.
Note: Some restaurants require you to park your ECV. You can always drive to your table & have a part member take it back & park it for you. I had to do this at Yak n Yeti as I can't walk more than a few feet at a time. (Hopefully these surgeries fix that for me!)
PARADES/FIREWORKS:
Find out in advance where the handicap viewing areas are and plan to arrive quite a bit of time (1+ hour) in advance to get a spot. We have seen many people turned away who showed up later.
CONCLUSION:
Scooters are a blessing to those of us who could not do Disney without them! While they present challenges all of their own, the pluses far outweigh the minuses.
I hope you have a great trip!