Welcome to the Disney Parks Moms Panel, Suzanne!
Your family sounds just like mine because there is always some kind of last minute mishap right before we leave for our vacation. I hope your daughter's uncle is doing well, and I'm pleased to tell you that a boot or a cast really shouldn't pose too many problems on most attractions. In addition to him being able to access most attractions, there are a lot of things that you can do to make his trip more comfortable as well. I usually walk about 10 miles a day when I'm at Walt Disney World Resort and that certainly wouldn't be easy with a broken foot. Check out what options are available for guests with
mobility concerns, and maybe consider renting a
wheelchair or an
ECV for your trip too to make it all a little easier.
Suzanne, I'm going to be honest with you and tell you that
Avatar - Flight of Passage might be difficult for someone with a cast or a boot on their leg to ride. You board the attraction in a forward seated position, as if you were riding a bicycle, and there is a leg restraint that comes up from behind you and locks into place around your calves. The restraint needs to be able to come down far enough to allow for a safe ride, and the boot may not allow for that or it may not be a comfortable position to have his leg in for a prolonged period of time with an injury. There is a test seat outside of the attraction that has the restraints on it so you can test and see if it will work for him before you get in line. You can always ask a nearby Cast Member to help you out and check to make sure that everyone will be safe when you're riding.
I hope this answers your question, Suzanne, and please let us know if there's anything else we can do to help you plan your magical vacation!
Jessica