We love late August at WDW. The crowds are low, the weather is great, the parks are open longer hours, and I don't have to take my kids out of school for it! We would be doing the same this year, but we are going to a cabin up north with my mom instead.
Until my kids are out of school, late August is where it's at!!
Now, if school wasn't an issue, I would probably pick early Feb, late Jan. Great weather, escape MN winter, low crowds.