and you will get use to it with practice, hopefully. I would absolutely consider going to a local zoo for a day trip and
renting a scooter and practicing there. Disney will still be harder with a scooter, but I think this is the best way to get started using a scooter. This is a good way to find out if a scooter will work for you, too. You don't want to find out at Disney this will not work. As an alternative you may have to think about pushing a manual wheelchair. I pushed my mom in a wheelchair for 5 years; she could never deal with an ECV; she had Alzheimer's disease. Some rides will fit a wheelchair like Buzz Lightyear or Toy Story Mania or the Jungle Cruise, but will not accept a scooter. I'm not sure, but I think you can transfer to a wheelchair on hand from Disney at some rides. The zoo scooter will be more like what you will be driving for a scooter at Disney. The store scooters are bulkier and harder to use than the smaller, portable rental scooters. The zoo scooter will be a good way to know if your mom will be able to handle and use a scooter.
My MIL had a little trouble using a scooter. She just wasn't coordinated enough. We did survive one trip with her by going on tortoise speed instead of hare speed with the scooter. We gave her a lot of help like parking it for her and getting it on and off the buses. We did the parks during the off times like early morning when the park would be less crowded. I was on guard with the traffic at all times through the parks.
Please be cautious on all counts; you need to keep your mom safe during the healing process. It may even be too difficult to get on and off a scooter for her without affecting her knee. You may have to assist her on and off the scooter. Get her to the ride and you or someone in your party should park it for the rides when you get there. You can use a scooter through the ride lines, but there can be a lot of turns in the ride queues. Getting on and off some rides can be a challenge. What comes to mind are boat rides. You need to take a pretty big step in and out of the boats. When we did Disney with my MIL there was someone on both sides of her for balance and lifting her in and out. Also, some rides have walking conveyors that move. On some rides this can be stopped and on other rides it cannot be stopped.
Spaceship Earth in Epcot is one ride where they can't stop the walking conveyor.
For a couple of Disney trips we concentrated on the shows, live entertainment, parades and fireworks more than the rides. If you are going in late November there will be extra Christmas shows to see, too. Your mom may have to sit it out if some of you need to do thrill rides and such. I would alternate the activities; so, she doesn't have to feel left out too much. I would have someone keep her company at all times if she has to sit out for a ride.
I'm not sure about your travel arrangements, but if you are flying you absolutely need to get a courtesy wheelchair for her in the airport. If you are car driving to Florida I think I would avoid the buses and use your car to get to the parks. There are portable, travel rental scooters that come apart into 4 to 5 pieces that fit in most car trunks. This is not hard to learn how to do. I would say as long as you mom is not over 225 pounds the smaller scooter should work for her. If she's tall you could have some issue with a small scooter. The area for the feet is not a big area.
Personally, I think you might be better and safer using a travel, foldable wheelchair. On sale you can buy one for $99 to $125 without tax. Travel wheelchairs can weigh on the light side around 15 pounds. Some wheelchairs can weigh 50 pounds; so, you have to be careful as to what you get. If you are car driving it will be useful to have a wheelchair for rest stops while using a restroom or eating and so forth. You can take one on a plane free of charge.
I'm not sure about your arrangements for the trip, but if you are 45 days out you can cancel the trip without penalty from Disney. You can change your dates to a better time. Everyone heals differently and your mom may be slow to recover; there's no way to know, right now. For airfares, you may have to eat a cancellation fee, but you can get air credit towards a future flight.