Welcome back to the Disney Parks Moms Panel, Jana! I must admit that I can completely relate to your situation. I also have a son who is absolutely terrified about getting wet. I remember the time we got off the monorail at the Transportation and Ticket Center in an absolute deluge at the end of a wonderful day, and you would have thought the world was ending because he got wet.
I checked the
Walt Disney World Resort Park Rules, and I did not see hair dryers on the list of prohibited items, so it should be fine. However, all bags, parcels, and strollers are subject to a search, and Disney reserves the right not to allow an item to be brought into the Park that may not be on the list. In some cases, Guests have been allowed to check their item at Guest Services if the Security Team deems it unacceptable.
If you'd rather not take the risk, rain ponchos are sold in just about every merchandise shop on Walt Disney World property, including the
Kali Cart in Disney's Animal Kingdom Park and the
Briar Patch in Magic Kindom Park (by the way, these stores also sell cute Disney themed beach towels, perfect for drying off). We can get our son on both Kali River Rapids and Splash Mountain ONLY if we purchase a poncho for him beforehand, and I will say that the Disney ones are high quality and can be used over and over- trust me, we have quite a collection now!
It sounds like you have a super fun trip planned, Jana! Remember to tell
Mickey I said hello (and Happy 90th Birthday)!
Eean