To feel more comfortable using a scooter as a newbie I highly recommend practicing on store scooters available at grocery stores,
Walmart, and so forth. Then, go to a local zoo for a day and use one there. One of the biggest hurdles at Disney World is there are people and kids that will dart out in front of your scooter; your reflexes need to be good to stop. Also, you need to use ramps where appropriate. You don't want to jump a curb with a scooter; the MK castle is an area of concern, here.
Scooter batteries are dependent on the weight of the passenger for how long they will last. Also, you need to shut off the scooter when viewing a show, parade, fireworks and so forth. If you are standing still there's no reason to keep the scooter on. There is a battery gauge on the scooter; so, you somewhat know how much battery power you have. Most scooters will last the day if you conserve the battery as stated. Often time we would take a mid-day break back at the resort and then we would recharge for the evening. That worked for us. If there's a need there are places to charge a scooter in the park; these areas are not obvious. You will need to probably talk with a cast member for a good location for recharging at the park. Keep in mind it takes a while to charge a scooter. Make sure you charge the scooter fully when you are sleeping for the night every day.
Keep in mind there are some tricky maneuverings with getting a scooter on and off Disney transportation. If you use your own transportation like a car then you have to deal with getting the scooter dismantled and in and out of the car.
If you rent at the parks, it's best to get there early at park opening to secure a park scooter rental. This is based on first come first serve. If there's a problem with a park scooter rental a cast member will help you get a replacement. But again, there has to be availability. Outside scooter rentals are a little tougher getting a replacement.
We have had relatively good luck with our scooter rentals. We have done park rentals and outside rentals.
We were able to enjoy Disney better by having a scooter.