We surprised our children (3 & 5)twice in one year. The first was our cruise in May 2011, which was horribly hard for me because I was making door ears and preparing FE gifts, putting things in a tub and buying summer clothes since my children are young each season brings new clothes. Then came the packing late at night just hoping they won't figure out we were going somewhere. FINALLY, we have a three hour drive to the airport and once we arrived at the airport parking we couldn't hide it any longer. On the way to the airport we told our children we were going on a
Disney Cruise...they were in shock, I am not sure they believed us. It was great and they were so excited for EVERYTHING that followed. Plus I didn't have to answer questions about when we were going for 6 months bc I was so excited my self not sure I could have handled the excitement of the two kids also.
We also surprised them with a WDW trip later in 2011, that one was great bc we had them so fooled. We were driving (22 hours) to get there and we kept printing and mapping out different ways to get there. My daughter found one of the maps and was playing around, I was thinking we are BUSTED, but instead she kept telling me we were going for a drive and this was the map. We just made a game out of it. So at 10 PM told the kids we had to go get gas and it couldn't wait. Mommy didn't want to go by herself

so Daddy had to come meaning you two in your pjs (sleepheads) had to be put in the car. I drove all night and they slept, not realizing we were driving through 4 states! When they finally woke up we told our daughter that we "were just following her map" she wanted us to follow it after all.

As we got closer we started asking her where she was sending us and she probably should have figured that out first before just giving us a map. The finally started seeing signs and my daughter was so proud of herself for giving us a map to Mickey. She still talks about it and tells everyone it was her map that got us there. VERY CUTE.
I wouldn't change either time, I honestly am wishing we would have planned the next cruise this May as a surprise but we didn't and the kids know this time around.