I will give you the run down on park attendance highs and lows. Although special events and promotions may influence Theme Park attendance levels, the following list highlights historic attendance trends throughout the year:
Lowest Attendance: January (except New Year's Day) until just prior to Presidents' week in February
The week following Labor Day until just prior to Thanksgiving week
The week following Thanksgiving until the week prior to Christmas
Moderate Attendance: After Presidents' week in February through early March
Late April through early June (except Memorial Day weekend)
The first part of Thanksgiving week
Highest Attendance: Presidents' week in February
Mid-March through Late April ("Spring Break")
Memorial Day weekend
Mid-June through Labor Day
Thanksgiving Day and weekend
Christmas week through New Year's Day
During regular attendance periods the Theme Parks tend to be the busiest on the following days:
Magic Kingdom Park: Monday, Thursday, and Saturday
Epcot: Tuesday and Friday
Disney's Hollywood Studios: Sunday and Wednesday
Disney's Animal Kingdom: Theme Park: Monday, Tuesday and Wednesday
This is a list that Disney World has generated based on attendance trends throughout the year and because I do not know when you are going, I thought it best to give you everything! Based on this information, I would go on the Sunday to Magic Kingdom if there are no special events listed for that particular day and you want to take advantage of the Extra Magic Hours.
Have a magical day!
Brigitta