Hmm, hadn't thought of that. I definitely wouldn't give money to a teenager on a bike saying he's giving it all to a charity.
Perhaps I could do it just as an awareness thing? Like riding my bike across Tennessee to raise awareness for Tibet or to support LGBT marriage or something? I have a lot of personal experience in Tibetan awareness things, I've worked in a bunch of Tibetan awareness rallies and have worked really closely with my school's Students For a Free Tibet club. This would involve no donations, just me handing out buttons, pamphlets, fliers, just stuff along the way. Maybe as a cool touch, I could give every city I visit a Tibetan flag to hang?