The parents have no conceivable case. It's not a violation of privacy since their dumb kids posted every one of those photos online first. He gave those kids a chance to make it right, and only one kid showed up for his announced clean-up day. Out of three hundred, only one took any sort of responsibility.
Parents who defend their kids against anything and shield them from any sort of responsibility have an increasingly common problem I've dubbed NMLA Syndrome. (Not My Little Angel) These folks are not going to be able to get their kids out of this one, as the cops have already identified all the partygoers. They'll regret not taking that first offer from the homeowner.