Working a potluck book club meeting in a couple hours and wanting a good versatile cocktail. Any suggestions?

A bit more context. I work at a fairly nice craft cocktail bar with a massive backbar. If it's a legitimate ingredient, I either have access to it or a decent equivalent. [Nothing crazy expensive plz] It's a pretty lowkey event (more than ten people would be surprising). It's after hours. The person who runs the book club actually used to work at the bar, and I replaced her when she moved onto greener pastures. It's kind of an everyone-knows-everyone affair.

So this isn't necessary or high pressure or anything, just a fun thing I wanna do.