I went to college in New Orleans (Tulane) and Louis Armstrong’s “What a Wonderful World was My Wedding Song.” I also listen to his music on a daily basis. I don’t remember any particular landmark associated with him while I lived there or since I have been been.
However, New Orleans is absolutely unlike any other American city when it comes to tourism. You may have been 50 times yourself in which case I may be preaching to the choir but I will point it out for other people reading. You don’t need a tour bus or informational pamphlets like you would in other cities. It is all just there and you can see and hear Louis Armstrong’s influence just by wondering around the French Quarter for hours or days. Most Americans cannot grasp the idea until they do it because it so so foreign to American tourism mentality and what is the norm for other touristy cities is inappropriate for New Orleans. All people need to do is walk and listen and have a great time. You can’t cover any of it in a weekend or even 4 years like I tried to.
I know this didn’t answer your question directly because New Orleans is not like other American cities at all and should not be viewed as such so they should question all assumptions before they get to far.
The influences of Louis Armstrong will simply appear all over the French quarter just from people sitting on a step and blowing his music to anyone that cares to listen (and for a dollar or two if you care).
For kids, a lot of the French Quarter walking tours are great and made me happy even having lived there for a while. My wife and I loved the Haunted New Orleans Walking Tours and kids should love it as well. The other French Quarter walking tours should be great as well and there are a number of them including the very popular cemetery tours.
New Orleans has much more in common with Venice, Italy than other American cities. Americans tend to get confused that there is a foreign city within the U.S. when they inquire about it yet everyone figures it out instantly. It happens on this board every month or two. I would strongly recommend the walking tours for anyone with children although the route may take 2+ miles over 2 hours which is doable for a 5 year old but younger ones may require a stroller.