Best night ports for a party couple on Caribbean?

We're cruising Carnival Sunrise out of Miami next October and trying to sort ports that are actually worth staying in late. Half Moon Cay feels too sleepy, Grand Turk nice but limited, Cozumel maybe too touristy. Want somewhere with bars, decent music, and a scene where couples can blend in without it feeling like a package trip. Any suggestions from people who've done this route? Prefer shore-side stuff that doesn't need a fancy excursion. Also if a port is good for people-watching and maybe a little flirtatious, but not cheesy cruise-club vibes, let us know.