construction, then be sure to have sections where they can do whatever they want to add their own unique features to the sand castle.
if you are making your sand castle on the beach then try to find a nice location that is slightly away from the crowds. you do not want people running in to your sand castle and knocking it over repeatedly. also, try to build your sand castle away from the water as the waves can flood your construction area and cause a lot of damage.
make sure that you have a decent sand wedge that you can use to help build your sand castle. this will definitely help 