Here are the offical holiday dates for the USA


Jan 01 2003, Wednesday: USA New Years Day [2003]
Jan 20 2003, Monday: USA Martin Luther King's Birthday
Feb 12 2003, Wednesday: USA Lincoln's Birthday
Feb 14 2003, Friday: USA Valentines Day
Feb 17 2003, Monday: USA Washington's Birthday
Feb 17 2003, Monday: USA Presidents' Day
Apr 18 2003, Friday: USA Good Friday
Apr 20 2003, Sunday: USA Easter Sunday
May 26 2003, Monday: USA Memorial Day
Jul 04 2003, Friday: USA Independence Day
Sep 01 2003, Monday: USA Labor Day
Oct 13 2003, Monday: USA Columbus Day
Nov 11 2003, Tuesday: USA Veterans Day
Nov 27 2003, Thursday: USA Thanksgiving Day
Dec 25 2003, Thursday: USA Christmas Day
Jan 01 2004, Thursday: USA New Years Day [2004]

May 26 is a Monday which suggest to me that the weekend before it might be quite busy!

Another suggestion is what time are the parks closing round that time? Disney usually know when they are going to be busy and the closing times is usually a good indication of that.

Hope this helps.