What kind of atmosphere does the OP want, is the question?

Depending on my level of intoxication my opinion of most places varies widely. For instance, places like Bouljis, Tasmania Ballroom, Dragon-I (well I've never liked D-I), etc etc are quite negative given the attitude of bouncers and often stuffy nature of the people who frequent it (or just that you don't see that many people smiling). Then again, when I've had about 5 rounds in me, I find that I can somehow tolerate most of them and have a good time. Other clubs include Play, Magnum, Prive etc. Lots will be 20 somethings, but there will be a lot more 30somethings than most think. People here party well past their 20s and sometimes 30s - it's just how HK is.

I think Lily and Bloom would be perfect, great cocktails, a nice crowd. Azure on top of LKF Hotel is also less stuffy but can be jam packed. One does get a lovely view on the terrace though. The top of the Ritz is nice. 001 is a nice sort of "speakeasy" in central, though you might have to book or hope they have spots. Quinnary on Hollywood Road makes a lovely cocktail but may get crowded, and Angel's Share is a great Whiskey Bar but gets packed so it might be a good place to start.

Walking LKF and Wyndham is a good idea, and if you are relaxed, Wanchai is a good spot too (something like the Pawn for an early drink and then hopping along and seeing the sights on Lockhart - at say Amazonia, Escape etc (live bands are usually ok to good).

If you want to go local - Minden Avenue in TST is close by your hotel (English level may not be good but the drinks fine and the crowd local), Lyndhurst Terrace is another idea (I dont know the club scene there very well however - I'm usually in Central).