Pretty irrelevant whether women are attached/ single/ divorced/ whatever. Whether or not they fancy him or hit on him is their choice. You have no control over any of it.
Bottom line is whether if he fancied any of them he would hit on them, or decide not to respond if they decided to hit on him.
Do you trust that he has firm boundaries around other women he finds attractive? Even when arseholed? Even when his mates are pushing boundaries and encouraging (either directly or by their own behaviour) him to?
Whatever the situation, it’s whether you trust how he would react to it, boozy, pressured or not.
Also make sure he knows exactly what you would/ would not accept. It doesn’t matter how reasonable or unreasonable anyone else thinks your conditions are, only you know what is or is not ok by you.
Do not ever assume that his definition of what is ok/ not ok when you are not there lines up with yours.
It can be a bloody eye opener what they think is ok if you’ve never had that conversation. Things can get out if hand.
It’s amazing how peer pressure, even assumed peer pressure, affects grown adults as well as kids. People will sometimes ‘go along’ with stuff in a group that they’d never contemplate doing if their partner was present, rather than risk looking like ‘a killjoy’ or ‘the odd one out’ or ‘a prude’. Especially if ‘what happens on this trip stays on this trip’ and you would never find out if nobody told you. I know a married guy (not my husband but he was on the trip) who ended up writing with a Sharpie on a young woman’s bare breast when she asked him to in a bar on a ‘lad’s’ holiday. His wife would have killed him. I’d have bet a lot of money he’d never, ever do anything like that, but the situation, booze and his mates egging him on meant his usual boundaries evaporated. Doesn’t excuse any of it, not one bit, but the thinking was “hell, she wasn’t there, wasn’t going to find out and I’ll look like a dick in front of everyone if I don’t , so where’s the harm?”.
Personally I’d rather stick pins in my eyes than be the ‘cool wife’ and go along with this kind of caper ever again, but then I have my own personal reasons which have no bearing whatsoever on your situation or anyone else’s. That’s my own crap to deal with.
Only you know what you can cope with, whether anyone else thinks you are being reasonable to impose those limits or otherwise.