I was initially skeptical, but I found myself sucked in - I've completed the quiz for the ipad. Furthermore, I now know a lot more about your product, because I had to look up the answers.
I think a major challenge will be, how do you keep people returning to the site? Once they apply for a few promotions and don't win any, what's stopping them giving up? Perhaps you could feature short (believable) interviews with the people who won, or for a short time after a prize was won you could have a banner on the site saying, "Mr Smith Won an iPad!". Something that will make people feel close to the winner, and make them think, "It could have been me".
I noticed that you must be over 18 to win the prize, but you also seem to be planning to spread primarily through social media. These two factors are opposed to some degree: the target audience that would be most excited about this site, and the most willing to share on facebook, are the younger teenagers. Personally, I didn't share on facebook because it wasn't something I wanted to be associated with. Would it be possible to say, you can enter but you can only receive a prize with your parent's permission?
Also, when I submitted the quiz, chrome brought up the red 'malicious webpage' screen, because content was coming from heroku not triviatise.com.