This is what we have done every May: I homeschool my oldest DS and my DD is in public and DS #2 is in preschool so this works for us.
Our school system lets out on May 25,'06 this year so I would probably pull my DD out of school on May 22, May 23, and the half day on May 24. They aren't doing any school work as grades have already been turned in by that time so she is only missing video watching. We would leave for WDW on 5/20 and arrive on 5/21 (we tow our camper so do it in 2 days). Then we would have several days before Memorial day weekend crowd and before the High School graduation crowds. We did go over Mem Day wknd this yr but compared to spring break of March '04 the crowds were nothing.
Now this is all hypothetical as this trip later this month will be the last one for a while.
What are your dates and ages of kids, if any?