You could send in a smart campaign using a random sample going to a percentage say 10% a, 10% b, then pick your winner and send out the email to everyone who hasn't receive it.
Or send it using champion/challenger. Check out this with the answer that I think will help you out. - Champion Challenger Sample Size
Thank you for the response. What I am trying to do is once my list has received the email, I want to resend the winner to the ones who never opened the email in the first go round.