We planned a trip in mid-Jan. I gave a present to DS for Christmas. I had a t-shirt personalized for DS that had seval characters on it in front of the castle, and it said my fantastic vacation at Walt Disney World, January 15th-22nd 2006. Then I put little mickey post it notes inside with details. One of them said, Animal Kingdom Lodge pool view room, another said my pirate cruise and the date and time, and another note with details of our ADR at Teppanyaki (his favorite restaurant) and another for the character meal we went to, and the last one was the details of the day we were meeting our friends whose son is he best friend who had recently moved to Fl. He was so excited because he had no idea we were going. It was awesome. He did have a couple weeks before the trip though. DD was only 11 months then.
The next time we go to WDW, I plan on not telling either child at all until the day of the trip. I think I can pull it off. I have the clothes ready to be packed and pack them without their knowledge. I don't know when that trip will be though.