I am not a regular at IAH - but a quick search turned up only one restaurant at IAH that is outside security - Stadium City Bar & Grill. It has one review on Yelp (not especially positive):
http://www.yelp.com/biz/stadium-city...-grill-houston
If I were you - I'd stick with the place at the airport (unless your aunt has a better idea). Since the primary point of the exercise is having lunch with your aunt - not a gourmet meal. That way you don't have to worry about traffic - finding a place - slow service at a restaurant - etc. And who knows. If you expect an awful meal - and get an ok one - you may even be happy with the dining experience. Robyn
P.S. I didn't notice you were an international arrival. In that case - definitely stay at the airport. Just check that this place is still open (it seems to be - but - since it's the only place outside security - doesn't hurt to check).