I just saw your trip report. Sorry your surprise didn't work out as planned. I had much better success when I broke the news to our kids before our Christmas 2003 trip. I also told them the day before we left. Once everyone got home from school I sat everybody down at the kitchen and gave them some good news and some bad news. The good news, "You aren't going to school tomorrow". The bad news, "You have to read this book". I then gave them a copy of Birnbaum's WDW for Kids. My DDs, 8 and 10 at the time, let out an ear piercing shriek once they realized what it all meant. My DS, 15 at the time, pretty much figured out something was going on (it was necessary to get a couple of his end of term exams rescheduled cause I was taking the kids our of school a couple of days early).
We camped at Ft. Wilderness in our 32' 5th wheel TT so we drove to Orlando from Dallas. I think the girls had finished reading their books before we made it out of Texas. It was a fantastic trip. I will say that being in WDW over Christmas is a really special time. We were there 12/19 - 12/28. It was quite a let down not being in Disney the following Christmas. We are going to finally make it back to WDW the end of July 2007. I am also already looking forward to a trip in Dec 2008. I will be able to book that trip the day before we return home from Ft. Wilderness this year. I'm thinking this may be another surprise Christmas trip.