There is that word "entrapment" again. This would definitly not be entrapment in the legal sense. Entrapment is when a law enforcement officer persuades you to do something you had no predispositon to do, almost to the point of pressuring you to do it. A mere suggestion is not enough. Just look at all the drug dealers in jail (can you get me a pound of marijuana?). In this case, you went to the web site on your own, not at the invitation of someone else. The classic definition of entrapment is "planting the seed of the crime in an innocent mind".
Men have been convicted of "transmitting pictures of a sex act to a minor". But the only time I have seen it is in connection with other charges where the older male pursues the contact. I really think you are safe by doing what you do, cutting off the contact and barring any further contact/viewing. But I don't know if there is a case yet to address your specific question. It's kind of along the lines of a minor using a fake ID to get into a bar or ABS. As long as the proprietor took reasonable precations, a prosecutor isn't usually going to pursue a charge.
And finally, I've done the same thing (open cam) so we'll go down together
