One question before I rant.  Why wouldn't you tell your friend that you hobby, given his desire to do the same thing?  Can you trust him to keep your secret?
    You cannot tell him about this site because, if he is half sharp, he will begin figuring out that you hobby and you seem to not want that to happen.  You indicated that he backed out due to nerves.  The question is whether the nerves came about because of concerns about getting arrested, or was he concerned about what his SO would think (if he has one).  Probaly the best thing that you can do is ask him questions about his case of nerves and only listen.  Don't give anything away about your activities, if you do not want him to find out about them.
    I remember the first time that I called an escort and went through with it.  It was a nervous situation, but a gorgeous brunette showed up and the nerves melted away as something else began to rise.  The thing is that I had spent a lot of time before that meeting looking over escort ads in the phone book and had come close to dialing many times.  Your friend has a need, the guess here is that he will go through with it soon enough.

Whatever you do, don't tell him about your hobbying, trust in a friend is a fraglie thing, particularly when their are women involved.