Why only 10 people, and if only 10 people, then why aren't you just talking to people you know rather than broadcasting it on HN? I think people can see through the fact that you are trying to gain interest by making it harder to access.
I posted on HN because i'm much more likely to get good advice on something like this here than i would get asking friends.
Usually people would just provide a site with info on how it works and a form in which they could provide you with an email address if they are interested.