I soent 3 days in NOLA in november 2013. I just happened to walk by the park in the French Quarter and saw their office, which was also referenced in Lonely Planet and decided to check it out.
I cans ay it was a great thing to do, the guide and the people in their store/office were extremely helpful. The explanations and tour were great, not too detailed as to be dry history, not too superficial as to be not informative.
We did a great walking tour full of anecdotes, questions and good humour.
I would totally recommend it if you have curiosity to know more about the past of the city.