Fountainebleu is OK that time of year. Shouldn't be to many crowds unless it's Easter weekend.
Personally we like Fairview-Riverside SP a few miles west of Fountainbleu also on the north shore. Just personal preference. And Morton's Restaurant in Madisonville is closer to FRSP. Morton's is a nice family restaurant. We've always had good food.
On the south side we like Bayou Signette SP at Westwego. Easy access, sites are farther apart. Shower house has always been very clean.
While in NOLA you really should go to the French Quarter. If you're not into the loud, smokey bars then don't go in them. But the people watching is well worth a visit. Very entertaining.
Lots of good places to eat in the city. Everyone has their favorites.
RE seeing where the Mississippi River dumps into the Gulf - you do realize that you can't drive to the end of the Mississippi River? You can drive down as far as Venice but there's still land and the river runs farther on. You'll need a boat to go on. It's just swampland from there.