Hi Carrie,
The Disney Water Parks are a lot of fun!
I really think you need to reach out to a cast member for an answer to this question. I would not want to give you incorrect advice especially where safety is concerned. I would call guests with disabilities only because they work with guests who need accommodations. Their number is 407-824-4321.
My instincts are telling me he would be okay with the fanny pack on ride with a tube such as
Teamboat Springs in
Blizzard Beach or the lazy rivers. I would think there would be a great resistance to him wearing the fanny pack on
Summit Plummet where you are only allowed to wear just your bathing suit. The fanny pack is more likely to be hooked on something. I also think snorkeling in
Shark Reef at
Typhoon Lagoon might present a challenge as well.
My daughter has an EpiPen and it could fit in the pockets of my husband's bathing suit. He has a suit with cargo pockets that would easily hold the EpiPen. Would this be an option to purchase a suit with cargo pockets for your son?
I would also talk to your son's doctor about his thoughts on this. He must have had other patient's with a similar need.
Wishing you a magical vacation!
Beth