Here's my opinion -- and it's diff from other people's responses, but it's just my opinion here.
1. Missing school teaches kids that school is less important that play.
2. Family time at WDW can be had on weekends, school holidays, summer.
3. WDW is not really "educational," it's visiting a theme park.
4. If there was a family event like a wedding/funeral/family reunion, etc. we would pull our DD out for those if necessary, but not to play.
We had this dilemma a few years ago with a cheer trip to WDW. Even though our DD is a "top" student, and she goes to a private school with a very liberal policy on this, we chose to pull out of cheer rather than have her miss a week of school. Why? Because I want her to know that school comes first, before play.
I agree with the others that 2 weeks is a long time. We went for 2 weeks a couple of times when our DD was in preschool. They miss out on projects, skills, and socialization with their peers. It really seemed like a long time to be away.
There are many kids at my DD's school who miss 1+ weeks of school because their parents get a business trip to China or Europe and decide to take the kids (it really is educational!). But those kids have a rough time "catching up" and many end up in tutoring, 2 ended up having to repeat kindergarten.
Of course, it's up to every parent to make that decision. We've decided to go during school vacations, even though it means more crowds and less days (due to both vacation days and the higher cost of travelling during school holidays).
Good luck with your decision. Remember, I'm just stating our choices and the reasons behind them. Other people can of course do whatever they please, including just saying that it's fun and they are going to do it. Justifying this on the basis of education or family time doesn't work for me.