I think it's a cool idea.

Here are a few thoughts:

I think it might work better in urban areas if you stuck to food/wine/microbrewery and art/museum/theater and city park type experiences. If you're going to do sports events, go as a spectator.

I think you limit your audience if you focus too much on the outdoorsy/physical stuff.

I think (at least initially) you should keep it to one adventure, as opposed to a choice of two and I think you might want to consider limiting it to twice a month until you have enough people attending to justify more than that.

I think you should try to offer a similar experience in each of your locations and a way for those who attended to share their experiences online so can learn about those other locations. A FB page could be used for that.

I think you should offer an option to pay per adventure.