Ask HN: Whats the best way to give away $25 amazon gift vouchers?

Hi,

I would like to give away $25 Amazon gift vouchers as a strategy to get people to use my bootstrapped startup

Whats the best way to give the vouchers away? I would like to give them to the fist 10 people who create public business plans on my site http://www.venturesocially.com but I dont want to be sued or get taken to the cleaners.

I want to limit the total spend to $500 dollars

What terms and conditions should I put in place to limit myself to getting in trouble?