There's a pretty wide range of party hostels in my experience. Some of them just have a bar that encourages drinking (maybe beer pong tables etc.), people still have to meet up on their own and go out. In the middle you have "social hostels" where they might do family dinner + volunteer led pub crawl, but you can still get a good night's sleep when you get back. Then you have the notoriously crazy party hostels where people are doing shots at 10 AM, people are hooking up in bathrooms and dorm beds all over the place etc. I like the middle ground myself but I've stayed at all three types, it's really just what you're looking for (and I think even a 30 year old would be fine at any party hostel if they are chill and not creepy about it).