Frenchmen street usually has a Halloween night block party/rave.
A lot of the performers do after shows at some of the other venues around town, so following a good act to a second show can be worthwhile if you think the listing is shit for the rest of the day/night... Bourbon is obviously going to be a mad house, but is a hallmark for a first time visit. If they're good with avoiding the tourist trap just hit some neighborhood bars/restaurants and meet some people.