We just got back...
We've gone the first week in March twice, and the crowds have been very manageable. The Saturday at the end of the trip was very crowded, but I don't know if that was a typical Saturday crowd, or if it was because some spring breaks have started that weekend. The weather is iffy...we had perfect weather this year, but the last time we went, the weather was very chilly for the first half of the trip.
Have fun with your planning.