Hi Beth! How fun that you're planning to run the Disney Princess Half Marathon!
One of the reasons I love Disney is that attention to detail and accommodation of guests is always at the forefront. The Magic Bands were designed to fit the vast majority of guests. The bands are adjustable so that they can be worn by anyone from a small child to a plus-size adult. I had a chance to try the bands with a group that included guests of various sizes, including some plus-size adults, and the bands fit everyone in my party. Keep in mind too that you aren't required to wear your Magic Band on your wrist. If fit is an issue, or you're like me and don't like to wear things on your wrist, you can attach your band to a lanyard, a belt loop, or your bag.
Did you know we have our very own
runDisney Mom here on the Moms Panel? If you have any questions about the Princess Half Marathon, she'd be happy to help you!
Wishing you a magical vacation!