OK, so nobody answered me.
Things I've found out:
Bergen county parks ban alcohol outright. If maybe some municipal parks allow it with a permit, I'm not sure
Somebody responded to my ad on Craigslist saying that Nyack Beach State Park up in Rockland County allows alcohol with permits. I have yet to go to them directly and check.
One place I know of for a bonfire night could possibly be the Closter Nature Center on Ruckman Road. Mark, the nature-bug guy who lives there, lets some regulars use the outdoor fireplace that's there built into the log cabin (which, again, he lives in and houses the nature center). I figure I could ask him one day if I wanted to host a campfire night.
Oh, and there's also the fireplace in the Ruins at the Alpine State lookout hiking area on the Palisades. But that you literally have to hike there, and I don't know if they allow night parking, I htink the park closes at sundown like many other parks.
Just some information should anyone want to host stuff like me...