"Grown Up" fun at Disney is everywhere. A lot of times my friends will talk about how WDW is for kids. I have to stop and think about it for a second. I often forget that the main focus is on kids. I'm too wrapped up in my own fun to even notice all the kids around. It becomes very easy to block all of that out.
As far as grown up fun goes, its great to grab a drink while strolling around. The only park you can't do that at is MK, but even there, I'll take the monorail over to the Polynesian or Contemporary and sit down at the bar before heading back over to the park.
A friend and I spent the day at DisneyQuest a couple of weeks ago. We decided things would be much more fun after a couple of beers. So, we would step outside and have a beer at the HOB outside bar, then come back in for a couple of games. We did that several times and before we knew it, the day was spent.
The point of my story is that if you tend to have more fun after a couple of drinks (and there's nothing wrong with that), there's no shortage of places to get them anywhere across WDW.