As to your weather concerns, expect anything. Last year on our last day at the end of February, the temperature didn't even get out of the 50s. We were freezing! Since it was our last day and the weather forecast before we left didn't call for cold, we were unprepared. Yep, sandals and shorts in the 50 degree weather with our bags in bell services at the Boardwalk!
As for the crowds, the week you're going is Mardi Gras week in New Orleans, so be prepared for a lot of people in Purple, Green and Gold. A lot of New Orleanians descend upon the world that week, but it's still very manageable. The upside is that Pleasure Island has some MG celebrations, so you'll get to experience that if you want to.
Good luck with your planning!