After reading all of these posts, I am definitely going to try this with my kids.
We are hoping to have a surprise trip for my parents' on their 70th birthdays in May 2003. This trip will have my sister, my brother, their spouses, their kids, plus my family all going with the folks. We have not all been their together as a family since the 70's.
We had been talking to the kids about this surprise for Grandma and Grandpa up until I read these posts. I mentioned the posts to my wife and we've decided to stop talking about that trip completely and are now saying to them that we are going to wait about three years to go again so we can do a two-week mid-Dec through Christmas trip. We're hoping they will have forgotten all about the 2003 trip by then. We plan to pick them up from their last day of school, start driving to the airport and, if they ask, tell them we're going shopping or something. We'll just have to drop it on them when we take the airport exit.