practice at home on store scooters. They're not the best and not exactly the same as a regular
scooter, but it will help to learn how to make turns and so forth. I would even suggest a day at a local zoo and using a scooter rental there.
If you are staying on Disney property, get a feel for the scooter at the resort; drive around and get use to it there before going to the park. If you are using bus transportation to the parks it can be a challenge for first time users getting on and off the bus with a scooter. You may have to help with this part. Sometimes, it's tough getting the scooter into the correct position on the bus for lock-up. My husband has lifted up a scooter at times to get it correctly positioned on the bus. He has good strength in his arms, not his legs. I think he feels rushed sometimes; because, you are first to board the bus and everyone is waiting for you to get done. By the way, first on the bus includes your whole party. When getting off the bus you are last.
For the parks, it would be great if you could surround her scooter and lead the way for her. People will dart out at the scooter and she has to be careful not to hit anyone. Some places like the The Land where Soarin' is located can be a challenge. To get the scooter on the level of Soarin' you have to use an elevator with the scooter. The Land is always crowded and that can make it hard. Some ride queues have many sharp turns and you need to steer pretty well sometimes. When you park for restaurants and such make sure you park the scooter out of the way of traffic. Park employees have been known to move scooters. There's a manual override they can use.
If you are renting scooters at the parks, then you don't have to worry about taking care of the scooter. If you are renting from an outside source (a cheaper way to go) then you will be responsible for charging the scooter everyday. Don't forget or you may be pushing a scooter through the park. For most of the Disney resorts you will have to get the scooter inside your room each night; unless, you have a car to store it and plan on using a car to the parks. Most portable scooters allow you to charge the battery off the scooter. Stay out of the rain with a scooter; seek shelter immediately if this happens. The electrical components can fail if there's too much water on them. Infact, carry your scooter charger to the parks in case you need to charge up the scooter. There are park outlets that can be used in an emergency. Most important is to remember to shut off your scooter every chance you have. If you are watching a 30 minute show turn the scooter off. If you are watching a parade shut the scooter off. If you are watching fireworks shut the scooter off. This will conserve your charge on the scooter. Finally, take your key for the scooter with you if you leave the scooter for a ride or eating or restrrom break and so forth.
Scooters are treated like wheelchairs at Disney. You use the handicap entrances to the rides and attractions when necessary. You are allowed to park them in the handicap areas for the parades.
Being with a scooter is by far the best thing to do, but there is some responsibility that goes along with using one. Your sister will love you for having a scooter.