Hi Mike,
Welcome to planDisney! Visiting Disney World in a boot is definitely doable. We have actually had to do this a few times and it is super easy to navigate. Luckily there are very few rides at Disney World where your legs hang free and are not secured inside a ride vehicle. This is typically where there will be issues with a boot for safety reasons.
Disney World has revamped its offerings for
guests with mobility disabilities to ensure they are supporting guests regardless of their mobility status. This includes a guide that guests can use to navigate which rides will require you to
transfer from a wheelchair and which ones
require a guest to be ambulatory. These are typically the only rides that cannot accommodate guests but since you said you are highly mobile, I don't think you will have any issues with them. The only ride that may be an issue is
Soarin' Around the World because your feet will dangle on this ride. Keep in mind that it will always be up to the cast member who is loading ride vehicles. It is their job to ensure that you are secured safely and will make the final call on whether or not the ride can accommodate your boot.
Lugging that boot around all day can be exhausting so don't forget that Disney World offers
wheelchairs for rent at the front of each of their theme parks. This can be a lifesaver on a long trip to Disney World when your leg is feeling a bit tired. It is an inexpensive and easy service that we love for those days when the boot gets to be too much.
Happy Planning,
Jenna