As the OP describes, this is a once a year event that is described as adults only. There is only one couple with a kid--the others don't have to adapt because one of them has a kid. No one is advocating dumping the guy as a friend, because keep in mind there are 363 other days of the year they can see him. I mean, OMG!! how will he survive missing one party?
This kid is old enough that I can guarantee if these parents are any kind of parents, the minute the first guy throws out a loud "F" word or the music is blaring at 2:00 am, you are going to get that look from the Mom. And then we all know what happens next: the guy disappears in the other room with said wife--and not for some lovin: 10 minutes later he emerges with that look of a dog that has been beaten with a belt: here it comes "Ah, guys Junior is sleeping and my wife was wondering if we could keep it down to a loud roar. Um, we can still party HARD (just said to make it seem like he still has one ball left), I just don't want him to be grumpy tomorrow. You guys understand, right?"
Like I said In my earlier post, as a parent you have to make a choice for what is best for your child and sometimes you have to just stuff your inner Frank the Tank to the side and say no. My wife and I have been together 25 years. We have a 14 and 9 year old daughter. We waited to have kids for almost 10 years to get those party years out of the way. During which time we went to Vegas twice a year, played poker every weekend, my wife loved fantasy football and we went to bars and movies all the time. We decided when we were 29, now is the time and we timed it out (because my wife has summers off her being a teacher) just the right mix of Coors Light for me and the irresistible rhythms of the COPS theme in the background (I work quick) and Viola little baby Jester #1 was on the way.