Cynthia,
Great question, and thanks for visiting planDisney!
When my girls were little, they had such slender wrists that everything would fall right off. On our first Disney cruise they had to get new kids club identification wristbands every day because they would fall right off, no matter how tightly they attached them.
Then came
Magic Bands! What you likely won't see when you view pictures of the bands is that you can peel off the gray exterior from end to end. When you do that, it shortens the band significantly for the express purpose of fitting on smaller wrists. My girls never lost their bands once, and the bands were never so tight that they felt uncomfortable.
Now I am not saying that a slap bracelet would be any less secure. But with my girls the slap bracelet is something they are inclined to play with. When they play with things, they lose them, that is a fundamental fact of life! For me, the choice is going to be Magic Bands every time.
BONUS TIPOne thing I love about the Magic Bands, especially when worn by kids, is the interactive element. When you are on different attractions you want to keep an eye out for some of the monitor-based technology around you. My girls love riding on
"it's a small world", even to this day. But the first time that the attraction signage said goodbye to them, by name, was a memory that will last forever.
Have a Magical Vacation!
Doug