8-Trax weaves 80s music into the mixes every night, so no worries there (other than the fact that you'll be enjoying a run of nice 80s tunes and... WHACK! all of a sudden you're back in the disco era, grrr.) Other than that, someone mentioned the Rock 'n' Roll beach club, which is pretty hit or miss, I think... great some nights, a graveyard some others. You're in luck if you're going on Thursdays, it's often one of the more fun nights to go to PI, IMHO.
Jellyrolls is definitely worth checking out, too, while you're down there.
You said spend some time with your drinking age friends... none of the clubs is really conducive to just hanging out, other than maybe the AC. For pure dance energy, I'd say Mannequins.