What really is the thinking here?

You're letting your girlfriend go on vacation with 4 other girls

There will be significant amounts of alcohol She will be away from home She will be in places with handsome athletic men looking for sex partying She will have her girlfriends with her who NEVER disclose secrets on girls trips

What kind of idiot does a man have to be to even entertain the notion of letting his woman go away with 4 other women to a foreign destination where you won't know what she will be at.

Women aren't unicorns. Never believe your girl won't cheat, she will the second she gets the chance and knows you won't find out.