These ideas are all so great! I look forward to trying a bunch of them in future years!
For our trip in May, our kids will be 6, 4 and 2 -- and I know that if they have ANY advance notice it will be driving all of us nuts. So we're planning to have the car packed and head to the airport first thing in the morning. I imagine we'll tell them when we arrive at the airport and they discover that we're all going on the plane this time! (usually it's only dad, going on a business trip.)
Oh, yes -- we've told the 2 older ones, who are already asking when we can go to WDW, that we'll talk about it when the baby is 5. LOL my dd4 will tell people "We're going to Disney World! Yeah -- when Sydney is FIVE!!" and is just as excited as if we were leaving tomorrow.