I vote wheelchair. There are enough in your group to share the pushing of a wheelchair. Even the 16 year olds can help. I would make a big, good fuss about who gets to push her next. Don't make pushing the wheelchair a chore, but a make it a joy. In regards to elevating her foot and traveling through the parks the group is large enough to walk in front of the wheelchair and to the side of the wheelchair if her foot is elevated. This should protect her wheelchair from anyone bumping it there.
ECVs at Disney can be challenging. Adults, as well as, kids dart out right in front of you. It really takes a quick stop at times not to run into someone. Ride queues have twists and turns that take some skill to maneuver a scooter; it's not a straight shot onto rides. Even at shows you have to be able to park it properly; you can't be just anywhere. As stated already pain meds don't mix well with a scooter and the driver. Everyone is different with pain tolerance, but if she needs more pain meds then most then this could make her sleepy and drowsy.
Renting a scooter from an outside source requires you to charge the scooter each night. Portable, travel scooters weigh around 90 pounds and they can be awkward getting in and out of a van or car. They do come apart, but the heaviest piece can go 35 pounds or so. Taking the scooter in and out of the resort takes some skill, too especially going in and out of the room. You may have to deal with an elevator, too. Next, you need to be careful not to run your battery down with a scooter. You need to remember for the whole trip to shut the scooter off when your in a show, or a parade, or fireworks and so forth. There's always a risk of running out of juice. If you are having long days at the parks this becomes even more critical. As everyone has stated a wheelchair can go on some rides and they can get closer to the rides then a scooter if you transfer. Most important you can take a wheelchair into a bathroom stall; you can't do that with a scooter. if she has a weak bladder this can be more challenging. Finally, if she gets sleepy you may need to take a mid day break and that means getting the scooter in and out of the van a few more times and so forth. Her handling the scooter can get her more tired, too. With a wheelchair, she could actually take a nap here and there in the parks.
I would consult with her doctor and make sure her doctor agrees a scooter would be okay. If it's okay I would practice at home when she can do it before the trip. There are free scooters in a lot of stores. You can even go to a local zoo for a day and see how she may do with a scooter. I still don't recommend a scooter. One Disney trip is not worth injuring the foot even more. A wheelchair should be safer. Of course, that is dependent on the pusher.
With the wheelchair option I would help the pushers by alternating activities with some rides, then some shows, then more rides and then maybe a parade, then even more rides and then followed by a meal for rest.
If she doesn't go on a ride it would be nice if someone stayed behind to keep her company and not make her feel like a burden. Again, making a big, good fuss about who gets to stay with her will make her feel better.
I would think about getting a handicap room if this is possible. You may be able to get this change. You can get a roll in shower accommodation and there will be rails in the bathroom to help support her. You can use the wheelchair in this type of room, too. You need to consult with the doctor as to what she should use to help her like crutches or a walker or whatever, as well.
Much of the success of this trip will be how well everyone is willing to help. If everyone is me, me, and me this could be a hard trip. There are considerations in her room to think about, too. She will more than likely need assistance with hygiene and putting on and taking clothes off and going to the bathroom. I'm in my sixties and I can't go the whole night of sleeping without getting up for the bathroom.