You mean driving? A recommendation on where to stay would kind of depend on what you're driving, as parking in the Quarter can be a little difficult with a larger vehicle. (If you're only doing one night, you would definitely want to stay either in the Quarter or the Warehouse District to get a good feel for the place.)
However, I've got to tell you that if you are driving from MO to FL, and you're only leaving one day extra, most of that day is going to be eaten up just in the extra driving. Going all the way down I55 and then swinging east on I-10 is definitely the long way 'round from Missouri. The more direct route is to go east from either STL or Cape, down I-24 via Nashville and on into Georgia & Florida via I-75.
As to Katrina Memorials, there are several. The official one is in the Charity Hospital Cemetery at the intersection of Canal and N. Anthony Street in Mid-City. (It is a Tomb of the Unknowns.) If you visit it, go early in the day; no tourist should be in any New Orleans cemetery after dark unless they are part of an organized tour group. There is also a really nice memorial wall down in St. Bernard parish at Shell Beach, but that's about 40 minutes south of the city.
PS: SWA had a sale last night of $60/rt from STL to MSY. They run deals from KC, too. I don't know where you are, but looking for a cheap airfare so that you can go another time might be a more viable way to get your DH his NOLA trip. Just FYI, the Christmas season is one of the best times weatherwise, and the cheapest hotel-wise and restaurant-wise, to go to NOLA. The trick is to be sure to leave by NYE.
