sorry, did'nt mean to sound glib about the booze and sex but blimey, they are 16, they should know all about 'sensible drinking and safe sex' by now.
my dd went to several festivals this summer, she goes into london most weekends, on the train, to gigs etc - she earns her own money, keeps to my rules, as in
1, keep phone on at all times
2, answer the bloody thing when i call it
3, eat before drinking
4, no fucking drugs (i have told her i won't be 'taking her for counselling' i will kick her backside till her nose bleeds if she does drugs, she is not stupid, she knows the consquiences)
5, when you decide to have sex, try and make sure it is 'meaningful' rather than a casual shag
6, if you get in any trouble AT ALL, PHONE HOME, we are always there if you need us
we have to let go at some point and treat tehm like adults - only the op can tell if her son is ready to go holiday with his mates, i can only speak from experience, my dd has been fairly mature since she was about 14.