Never been to Jazz Fest. I do play jazz clarinet, and New Orleans is an absolute mecca for that, as I'm sure you're aware if you're going to Jazz Fest. I highly recommend Preservation Hall if you haven't been there. Last time I went, you could either buy tickets online or stand in line super early to get in (I did the latter...got there an hour early). You can buy beer next door and bring it with you, but they don't sell any in Preservation Hall. And while you're there, if you have the opportunity to hear Dr. Michael White play, either at Jazz Fest or out on the town somewhere, do it (he's a clarinet player, and I freely admit my bias!).
Camping around New Orleans is tough. If you keep your standards low, you can find something nearby...although I suspect that they will all fill up during Jazz Fest. We don't particularly like RV parks or campsites that are jam-packed together, so we tend to go further out. The last time we camped near New Orleans, we opted to stay 2 hours away in Breaux Bridge. Good luck, and if you find anything worthwhile, please report back!
Oh, and the National WWII Museum is *superb* and worth the time to go see.