Definitely rent off-site if you can. We go to DLR every year and have two disabled people in our group. The first two years we needed a scooter, we used the DLR scooters. They were not very useful. The main problem is they ran through their charge way too fast. They usually worked well enough for shorter days, but on longer days the charge sometimes ran out. Usually you can exchange it for another, but one time they were out of scooters and we were out of luck (with no refund). So for half the day we had no scooter.
Now if you rent from The Scooter Store and the thing dies, they bring one right out to you! They promise it won't take long and it doesn't. We never had the charge on theirs die (I've never even seen the charge go down!), though we had a mechanical problem with one. The scooter was traded out within a half an hour. We've used them for three years, renting two at a time. Our trips are long, so we had them between nine and twelve days. They are great! If you rent the DLR scooter, you get a poorer quality scooter and pay more for it. You can't use it to get to and from your hotel. And you can't go into Downtown Disney with it. Since Downtown Disney is quite a walk if you have a disability or pain issue, having the scooter is very nice.
If you rent from The Scooter Store, then ask them for a scooter with a head rest (the model we rent has some with and some without). If you do that, you can hang a backpack or bag over it, which is really convenient. Since we go to DLR in the cooler season, it gets warm by day and sometimes very cold by night. We just pack warm clothes, put them in a backpack and hang it on the back of one of the scooters. It's also a nice way to carry around small purchases. Another way we take advantage of the scooter is that we carry around an insulated jug with ice water and keep it in the basket. We save a small fortune on bottled water and we always have nice, icy cold water with us.
Have fun!
