I did the Mardi Gras cruise with Celebrity Reflection in March this year.
It was quite some experience, you get both Mardi Gras and the Caribbean in the same cruise.
It was nice cruising the Mississippi river daytime, but it was rather foggy. I made a time lapse with my GoPro of the river-cruise that you can find in a link below.
We had sunny weather in NOLA, but it was cold. The day before we arrived it was 74F, when we were there it was 36-38F and the day after we left it was back in the 70's again.
If you like parades there is a lot to see. We didn't do Burboun Street at night as we thought it may be a bit too wild there.
It was, of course, a lot of people everywhere and not too easy to get into restaurants.
We had a day ticket to a grand stand during the last day parades. It was very nice to watch, but a bit cold. We were standing there for more than 8 hours.
If you go I recommend to buy tickets to a stand. Ours were at the Lafayette Square (stand B) and they were right in the center of the "action" (with the main stand at the opposite side).
Of course you can see the parades from the road side too in some areas, but it's nice if you cen get a bit higher up and the stands are a bit closer to where the ship dock (I think).
I would not hesitate to go again.
Link to the time lapse from the Mississippi cruise (about 1/4'th of the river cruise and arriving in New Orleans):
B2B in the Caribbean, Jan-Feb 2020, Vancouver to Tokyo, Tokyo to Singapore..Sept 2020. and Transatlantic Nov 2020 .Just did Sydney-Hawaii in April-May, making up for the last 3 years that I hardly cruised at all while helping to take care of my younger brother.