We did exactly that with a similar incident and the local FBI Cyber Crimes folks told us that they couldn't help us because they were entirely dedicated to potential terrorist activities. So, I would say "contact local authorities and play it up as a terrorist act" if you want any help at all.
Or, you can somehow work into your complaint about how you are just trying to "protect the children". Our local Cyber Crime agent, while stating something similar regarding terrorism, also told us that in order for them to even begin to investigate, the total damages would have to add up to $10K or more. I'm not entirely sure how every type of perceived criminal activity translates into such high monetary loss, but this is what we were told. Earlier this year, we were instructed to submit information to the IC3: http://www.ic3.gov I've not yet had the need to use this site, so I can't vouch for its usefulness. I imagine that if Joe Consumer knows about this site, they get a lot of the aforementioned crackpots filling out complaint forms. Does anyone else happen to have experience with the IC3? -evt