You need to find out if your insurance company will cover you to tan children and IF they say yes you can tan them what do they require you to do beforehand, during and after the tan?
Do they need you to skin test before, do they need parent/guardian in the room at all times do they require you do anything exra as aftercare?
When I have given tans as raffle prizes it has always been to over 18 events but after my last donation I had a call asking me to go and tan a 16 year old who had been given the voucher from her gran (who had won it at the adult only event). I apologised to her and told her I couldn't do it as my insurance doen't cover me (it is my personal choice not to treat under 16) and that she would have to pass the voucher on to someone else or I would take her details down & would keep the voucher valid unitl just after her birthday for her.
I got a phonecall the next day from her brother who had been passed the voucher and I booked him in and tanned him.
At the end of the day even if a child wins it that doesn't mean you have to tan them - you can set terms & conditions that exclude under 16/18 and if asked just state your insurance doesn't allow you to treat them.