Hi Jennifer!
As a person that has shattered many "shatter-proof" cell phone cases, I not only appreciate your question, I understand it all too well.
I love how proactive you are being with your planning and I'm so excited to see you will be at
Walt Disney World Resort in a few short days!
As you are clearly aware, the
Walt Disney World Resort Property Rules state, "All persons, bags, parcels, clothing and other items may be subject to screening/security checks." I chatted with a Cast Member and she reached out to the Security team. They confirmed that your arm band is classified as a bag. So - as you put the finishing touches on your vacation plans, you will know you will need to pop through security so they can take a quick look through your arm band. I'm one of those Guests with a backpack with multiple pockets so I'm impressed with the way you do the Disney Parks!
Thanks so much for sharing your question with the Disney Parks Moms Panel! Enjoy every magical moment of your Walt Disney World Resort vacation!
Kari