That is the greatest thing to experience, isn't it? I got away with it twice - once on the way back from the cruise - they didn't know we were then going to the parks, but they were so exhausted, we had to wake them up when we hit the Magic Kingdom sign - and they were instantly awake! Then, like you, we did the whole "secret trip" trying to pack covertly - told them we were going to Atlanta. We hit the sign that said Daytona Beach and my son said "hey....where are we really going??" I love that wonderful element of Disney surprise. Have a wonderful time!