I just found your question, so I hope i'm not answering to late.You can rent a small bus with a good sound system and a lot of tunes and ride through the streets in a party bus, down Commercial Street, the main drag of PTown (pun intended, of course) Contact the Funk Bus at 508 487-0111, see website at thefunkbus.com Even last-minute arrangements can often be made.
If you want a really unique experience consider the sunset dune tour. You'll ride in Chevy Suburbans in a "wagon train" along with other folks in other Suburbans , about 6 or 8 passengers per vehicle, and have a guided tour through some amazing countryside. You'll stop on top of a huge dune with the folks in other vehicles for an amazing view, time enough to have a glass or two of wine (check and see if they allow glass containers, a box of wine might be better) and from there the wagon train proceeds down onto a fairly private stretch of beach and your party can have a spot away from all the others, whether you have 6 people or 20 (or more) and you can relax on a beach blanket (provided) and have a little wine and cheese or bring a whole dinner with you to enjoy while you watch the sunset over the Atlantic Ocean, or the dune tour company can bring a whole clambake along and serve you a full lobster dinner on the beach, other dinners available if someone doesn't want seafood. You'll spend about an hour on the beach and then drive back over a dune into town, finishing your tour right across the street from the Governor Bradford, where you can order drinks and join in with the karaoke crowd led by a drag queen., but a crowd that's often fairly straight, and always fun, whoever shows up.
You could also plan to see Miss Richfiekd 1981, one of the funniest shows on the planet, at the Crown and Anchor at 9 PM, serving drinks during the show. You may want to reserve a section of the porch or patio for your group to have dinner there, and they will reserve a section of seats for the show for you as well. Call the Crown and Anchor at 508 487-1430. The Crown is a hotel/show bar/restaurant/nightclub complex all in one. Just avoid the Vault. You and everyone else would be very uncomfortable if you walked into that bar.
Sounds like you might be planning to stay a night? Or two? Ask about the Sizzling Summer Special when you call the Crown and Anchor, though you're probably planning a weekend, which will be harder and costlier to arrange at this late date. Try the Harbor Hotel, a more mixed crowd where you all may be more comfortable hanging around the pool than you would perhaps be at the Crown's pool. The shuttle bus goes right by Harbor Hotel about every half hour to bring you back and forth from the center of town where the Crown and Anchor Complex is, so no one has to drive after drinking.,and they have parking for your cars at the Harbor Hotel, which the Crown does not.
So if you're here for a weekend, dune tour and dinner on the beach (whether you take your own picnic or have the dune tour clambake) followed by karaoke at the Governor Bradford one night, and dinner and a show and the wave bar after, all at the Crown and Anchor on another night, or somewhere in there you might want to rent the Funk Bus. The Surf Club is another spot where you'd probably enjoy a few drinks, sometimes with live music, but don't eat there - decidedly average (or worse) food at a staggering price, but a less gay crowd at the bar and probably fun for you.. The Squealing Pig is another possibility for dinner and drinks, an Irish pub with good pub-style food, and after a few drinks you could move up the street to the Governor Bradford for karaoke and more drinks, or on to the Crown and Anchor to see Miss Richfield. If you stay a night or two you may want to consider hiring the Funk Bus so no one has to drive after drinking. Hope this is helpful. You can read my blog, TheYearRounder's Guide to Provincetown, found at ptownyearround.com, to read reviews of other restaurants and shows. Have fun, and best wishes to the bride! TheYearRounder