4. Easter Sunday
Easter is a bit of an odd one for this list. Given the roving nature of the holiday's annual date, depending on the year you visit it may be a perfectly easygoing trip, or if you're less fortunate it will fall around the same time as many students' Spring Break vacations and you'll be in for a sardine-y time.
Of course, it probably won't be quite the level of insanity that is Christmas or New Year's Eve, buuuut...we'd still recommend hopping over to another park on this one. Maybe try Epcot instead.