I've been down over several holidays (Memorial, 4th, President's, Valentine's). The actual weekend of the holiday, especially Monday holidays, will be quite busy. People close to WDW come out for the long weekends and fill the Fort. By Tuesday, things drop off considerably. The Fort will be full over the weekend, but much more open by Monday night. I check in on Tuesday after Labor day this year specifically because I want to miss the crowd. The crowd calendar I normally use has the weekend in the parks as 7/10. Labor Day a 5 and the rest of the week 3-4.
j