I selected both April 15 - May 31 & June 1 - August 4.
Why:
June 1 - August 4: We prefer not to take the children out of school, and DW is a teacher and only gets 2 personal days a year (and can save up to 2 more from previous years, for a total of 4). We don't go after August 4th, because both kids are in marching band, and band camp usually starts around the 10th - 13th. We don't go during Easter because we want to be at our home church, and the children don't get a lot of time off. We don't go during Christmas because, again, we like being at our home church, and because it's so crowded. Plus, we feel there's something just off about being in the tropics during Christmas.
April 15 - May 31: Every four years or so, the high school marching band does to Walt Disney World. This year, it was late April. DW saved up personal days and we took a short trip to watch the band.