Decorating Waistpacks (fannypacks) for kids?

[LSUmom4kids]

I bought 3 navy blue waistpacks with water bottle holders for my kids (DS10, DD7 and DS5).

Please give me some easy ideas on how to decorate them so that they will like wearing them, plus so they will be able to tell them apart.

DS10 is into all sports
DD7 is a "girly girl"
DS5 is into cars, motorcycles, bikes, etc.

I cannot sew, but I do have a new hot glue gun!

Whatever I do, I want the designs to be waterproof, as I'm sure the waistpacks will get wet - we are going to WDW in August.

Okay, please give me all your great decorating ideas!!