Depends on what you would like to do. Some venues, like the WWII museum, are all-day. Same with plantations. You can find self-guided tours of the French Quarter, Garden District, and more. Ghost tours are popular.
February weather in NO is unpredictable. Cold and rainy days sometimes, cool and dry at others. Crap shoot. When you get closer to your arrival date:
www.bestofneworleans.com for local events
Music: wwoz.org
On the New Orleans board I recently posted a list of restaurants I like, in or near downtown. There are lots of others.