My dc will often say " Can you say I'm not allowed to...." so that they can blame whatever it is on me, and not 'offend' their friends, or seem uncool.
I'm more than happy to play the bad guy in these situations.
We've always allowed them to taste a sip of alcohol (well, from about 6yo) on the rare occasions we have a drink.
We've never made a big deal about it and have always been honest about why people drink and the possible consequences of over doing it.
As such ours haven't shown that much interest in it, and in general, (and certainly always until the last year or so), they've always been put off by the 'disgusting taste' (their words).
My oldest only really started going to parties where alcohol was supplied by parents at 16.
At 16 here they're allowed to drink cider/lager, and if I'd known/ trusted the parents or trusted the friends I may have let her have a couple, but I didn't.
Instead I bought her some alcohol free Kopperburg to take with her and although she wasn't completely happy (more about what it would look like to others), she understood that if she showed she could be trusted to stick to our rules she'd be given more freedom and possibly be allowed the odd cider in future.
I later found out that the parents had bought vodka, etc, which I wasn't really happy about, and that there weren't even any adults present.
Although she'd stuck to our rules, I said in future, I'd prefer it if we hosted the parties here, rather than somewhere else, but there'd be no hard liqueur allowed, and everyone invited would have to tell their parents that there would be cider available at the party.
Since then we've hosted 3 or 4 'parties' (they're now all 17/18), and haven't really had any issues. My dc makes it clear that no one is expected to drink and we provide plenty of non alcohol choices as well as some cider/beers. I also provide food first so they're not drinking on an empty stomach, and I always stay downstairs. They have to come down to get drinks, etc.
Doing this I've found that none of them over do it, and generally only have a few each. They actually seen to prefer having rules and it being made clear that no one has to drink.
My youngest isn't allowed to drink as they're still only 14, and to be fair they don't really like the taste so far (when they've been allowed to try). The friends they have aren't interested either, which helps.
My oldest has been allowed, under supervision, to drink cider from 16, eg, 1 bottle at meals out where the restaurant allows it (some have their own policies of not under 21, for example), and at parties we hold or where I personally know and trust the parents (only 1 of them, and they've only hosted 1 party) and they're now 17 and have a pretty sensible attitude towards alcohol (so far).
I don't think yabu are all, and I've also been shocked at how little most parents seem to care.
I have always allowed mixed sleepovers if they want to, but they'll all sleep in one area, and everyone gets changed separately in the bathroom first. I do check on them and my 2 know that if there's any inappropriateness, or if they feel uncomfortable that I'll deal with it (They just have to text/tell me), but tbf it's still all very innocent atm.