I was in NOLA the same weekend last year and hit upon the following haunted house, which was pretty good as it is set in a (former?) working mortuary. You can take the Canal Street streetcar to the location: http://themortuary.net/ They let in groups of 10 at a time and it takes about 25 minutes to get thru it.
Personally, I would not take any of the ghost tours. My party did one once and we wound up walking off the tour about 20 minutes in...snoozefest. I think it's all about the tour guide, and we apparently had a dud.
