Another way to structure it would be, for example, $50 off review special with $50 off a 2ed visit after the review is posted. Small discount up front to catch the eye of guys. do it. If he was happy with the visit, the extra for a 2ed visit might get him to actually write the review.
As I said, be creative. No right or wrong way to do it. Just remember what others have said. Many, if not most guys will never post that review.