To be honest with you, I don't think you should talk to him about it, and I think you should let him go.
My reasons are to do with my personal situation. I am happily married, and I would let my husband go anywhere he liked on holiday, if he wanted to, but it hasn't always been like that. At the start of our relationship i didn't trust him, because I've also been cheated on in a past relationship. I used to get moody when he would go places because I was worried about what would happen if I wasn't there, sometimes he wouldn't go out (which I feel terrible about now) and other times he would go out. But overtime this has made me realise, trust can't be given, it needs to be earned.
The hardest part about this earning process, is that you need to allow him to go out and earn that trust. So let him go away on his lads holiday, if something does happen you'll find out sooner or later, and if he does cheat on you, dump him. Do you really want to be with someone that can't stay faithful to you? At least this is giving him the opportunity to see what happens, because let's face it, if he is going to cheat, he will do it regardless of this lads holiday. If he doesn't cheat, you'll trust him more. It took me about three years to 100% trust my husband, but if every time I moaned about him going out somewhere he stayed at home, I probably still wouldn't trust him because he would never have that opportunity to prove himself. I know for a fact my husband would never cheat on me, and has never cheated on me.
You just need to let him get on with it, if he cheats then that's just showing you his true colours and it will be a blessing in disguise, you won't have to waste more of your life with him.
If he doesn't cheat, you will start building up trust, and every time he goes off somewhere you will gain more and more trust in him. Once you realise you 100% trust him is such a comforting feeling, you will be happier and it will make him happier you're not nagging him when he goes out. It will be a hard and worrying thing to do, but you need to do it. And as Fluffbags said, it's got nothing to do with 'horny little sluts', if a single woman wants to sleep with a man that's totally fine, the women aren't to blame. If your boyfriend cheats, then he's the 'horny slut' for not being able to keep it in his pants when he's in a relationship, and you'd be better off without it.