Blindfolding your children is not in the official manual but around here we stand by it. All morning I kept the boys in the basement while building up the surprise. We even ate lunch down there while, as far as they know, Dad prepared the surprise.
When the blindfolds came off they looked more stunned than anything else. Guess where we spent the afternoon?
We put this off for years due to the move but finally made the outdoor play set plunge.