Where are you staying? Will you have a car?
The streetcar ride down St. Charles is fun and shows off a ton of great architecture. There are also Garden District architecture walking tours that may be interesting - I've never been on one. For food, Jacque i mo's on Oak Street is a winner, although can be somewhat pricey. There are tons of places with great music... Snug Harbor and other music clubs on/near Frenchman, and the Kerry Irish Pub on Decatur has a nightly band with no cover. The Maple Leaf bar on Oak st. has nightly music, too. You can get nightly music listings at offbeat.com.
No kids, what a treat! You picked a great time of year to come. The weather here has been gorgeous... high 60's during the day. Perfect!
Let us know where you're staying and I'll try to post more ideas. Hopefully, you'll get some more responses, too. Sometimes this forum is a little slow...