Welcome back to the Disney Parks Moms Panel, Sean! It's great to see you are headed back for more pixie-dusted adventures! I am sorry to read of your daughter's issue with her foot. I certainly understand her predicament. I injured my ankle just a week before my annual summer trip with my sister and ended up being in a walking boot. I was so worried about how everything would go, but it turned out to be one of our favorite trips!
I am not sure how old your daughter is, but consider
renting an ECV or wheelchair for her to use during your trip. There is a lot of ground to cover at Walt Disney World Resort. Covering those miles on foot while wearing a walking boot or using crutches - not magical! I tried to do so for a bit, but my altered gait pattern really had my entire body hurting after a while. I ended up renting an ECV from Buena Vista Scooters and it made a HUGE difference in my enjoyment of the trip.
I looked over a list of all theme park attractions and do not see anything that includes a restriction on casts or boots. On Avatar Flight of Passage, there are leg restraints that come behind the calf area of your legs. These restraints do not press hard on the leg, but it is just something of which to be aware. I did not have any problems with those leg restraints while wearing my walking boot. My sister and I rode pretty much everything that week and there were no attractions I was restricted from riding or even had difficulty riding.
If you are heading to one of Disney's Water Parks, then that is a whole other discussion! Since she really would not want to get her boot soaked, I am sure you are not planning to head there this time. Just understand that the majority of attractions at Disney's Water Parks would restrict her from wearing the boot while riding.
Thanks again for stopping by and please let us know if you have any other questions!
Brandy