New Orleans in Manhattan?
Jimmy's no 43 is doing a Mardi Gras special. They usually put on good events so it should be fun.
I also recommend Acme. It has everything as far as New Orlens food goes- gumbo, po boys, etc and all the Abita beers and mean hurricanes. I love it.
I'm thinking Mara's Homemade will likely be filled with N'awlins ex-pats. But that is probably the most "appropriate" spot for Mardi Gras if you can get in.
Jimmy's 43 seems might be a good alternative. They are supposedly coming up with a special Mardi Gras night, exact details have not yet been decided.