and I suspect that being here will also act as an extra level of accountability, though there are no easy solutions.

I'm struck by your comment:"I don't know how to follow up a friendship and scared the parents will be suspicious." You might want to follow the story that HFJ has told us over the past 6 months of how a casual contact at a youth club that he was a volunteer at has turned into a full on YF. The start is back here:

http://cblf.org/messages/60362.htm

and he has struggled with those sorts of issues - you might find it helpful to see it worked out. And yes, I guess we've all been there; the value of this is that you can watch it unfolding.