That's the second weekend of the New Orleans Jazzfest. I think you can forget about any cruise specials and most discounts anywhere. Many hotels are booked and some may have minimum stays.
New Orleans Jazz & Heritage Festival // April 29 - May 8, 2011
Every year, hundreds of thousands attend.
Perhaps one of the hotels blocked by the festival will meet your needs, but there are unlikely to be any real bargains to be found downtown or in the French Quarter:
New Orleans Jazz & Heritage Festival // Travel
You might try Holiday Inn Superdome, Mariott Convention Center, and Hilton Riverside to see if they have some sort of cruise parking special, but I would be surprised if they did.
The less expensive option would be to stay out of town and park at the port.