I have had the same problem. I responded to the first one to politely tell them I wasn't interested, and that they shouldn't be trying to find romance in such an unsafe way, but they keep contacting me again. I will never do online dating because that is a stupid and dangerous way to "meet" someone for romance. I think the site needs a rule about this:
"No unsolicited date mail contacts."
Any one violating that rule should be kicked off the site. This should help. What bothers me even more is that the person involved has continued to send me these messages, in spite of the fact that I politely told them I wasn't interested, and that I didn't want them contacting me again. I even found one in my site mailbox earlier today, and just deleted it without reading it. I think if it happens again I will make a complaint post with their contact info on it, to expose them, and warn people against this person.
I hope you don't get any more of these creepy things. It does seem like they are someone who is up to no good. Fortunately, I am not very gullible. Good luck with your kid's situation.