[Ian Grant]

You need reporting to the Met, they asked us to report any suspicious photographer, I've even seen the posters here in Turkey.

Just do it, but with permission from an organiser, tell the organisers that if any parent has an objection they can withdraw their child. Actually it's up to them to ensure that under 18's aren't exposed to paedophiles.

I should have said I regularly shoot images of under 18's and the occasionally under 16 for work, I had to have police checks to work with minors, but as long as they bare supervised by a responsible adult while you take the images you have no legal problems.
Ian