This is an incredibly hard idea. Think about the average early adopter: he/she is going to look for adventures close by, or in a certain location. What are the chances they will find a bunch of choices? It's a classic chicken and egg problem.

What you can do.. although not as sexy is to limit this to 1 specific location, say Hawaii. I know there are a couple of companies that are making nice money by referring customers to certain adventures in a specific location (you never hear them in Techcrunch or HN, mind you because they not "sexy")