It's very akward, but to a certain degree, I feel that you have to let them get on with it. Give them a little bit of trust. If they're nice lads, then I'm sure if you give them an inch, they won't take a mile.
I'm 15, and I went on holiday in April with my best mate (also 15) we didn't get alot of responsiblity, so we ended up just asking friends we met on holiday, who were all inclusive to buy us drinks. We're also going on holiday in 3 weeks, and will probably do the same.
The way we sorted it out with my mum, is that when we arrived back at our room, we'd knock on her door, just to let her know we were back. It let her sleep a little easier at night.