That was my idea as well.
I'd recommend adult signers - both for clarity and legal reasons.
If you are going to use any under 21 signers on your website you'll need to have a written extensive waiver from from their parents waiving ALL rights now, and in the future to anything related to the site, any images or videos and any profits etc. (When I was doing a large fundraiser I had a lawyer write the waiver form so that we where legally "covered")
P.S. Thanks Dogmom for understanding what I was trying to say in my previous post.
