As someone who's researched this time period and is about to head out on a quick trip end of February / early March: my understanding is that the parks are going to be very crowded for the whole month of March, other than the very first week of the month (1st-7th) where crowd levels will be moderate. Various spring breaks are scheduled during this time. If you're looking to avoid crowds, March 10th would not be the time to go. You also need to keep in mind that the general trend this year has been to see higher-than-anticipated crowds. Whether that's because of weather or FP+ or the economy or random chance is a topic for a different discussion. But my point is that, even in a "good" year ("good" in the sense of crowd estimates are proving to be overly aggressive), March is an extremely busy time of year to go. And we are in the opposite of a "good" year (same sense), we're in a "bad" year insofar as a lot of people are being drawn to the parks beyond normal expectations.