Here's the completed mustache, I'll post the pic of the kids once they're done getting ready!
To make: 1 Roll of 1" White craft foam - 1 Roll of (Your Choice Material) Decorative Material for Strap - 3 Cans Black Spray Paint - 1 Super cool dad who can eyeball a giant mustache, cut it out and sew on the straps

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Edit: And here they are! A Mustache, Ninja, and Izzy the Pirate!