The Aquarium is really fun and takes a few hours. It's just off the pier (where they launch the dinner cruise ships).
Get a muffalata at the Central Grocery Store. One should be enough for 2 people

, and if you get it to go, you can have a nice, inexpensive lunch by the water.
Meterie (sp?) has some cool shops, and it's got a different feel from the quarter. We drove last time we were in New Orleans, so that wasn't an issue. The trolley goes to uptown and the garden district, many nice things to see scenery-wise.
My folks (which are avid drivers) went a little further out and stayed the night at a plantation and had mint julips. A little on-line investigation should get you names and prices for plantation stays. They can get pricey at the swank places.
And of course, eat lots. Drink lots. Debauch a lot. It's New Orleans.
Edit: And the music! If you like blues and jazz, there are tons of music places from holes in the wall to more touristy places like House of Blues.
And if you are adventurous, find the Jerusalem Deli. The Best Mediterranean/Middle Eastern Food ever. If you are lover of the falafel, hummus, baba ganoush, and of course the savory meat/mutton dishes, this place is heaven. It's on the trolley line on Carrollton.
--Ok, so I failed my reading check. I'm not a local to New Orleans, although Joe lived there for 4 years and the Jerusalem Deli tip is pure gold.