Shadows never lie, and if children are taught that at a young age you can sometimes extract information from the children you might never get.
I've told my kids if they don't tell me the truth when I question them, I'll just ask their shadow because they know that their shadow is always with them. God gave them shadows so parents don't have to hover around them all the time. It works from about age four through about 7 or 8 depending on the child.
Learning about shadows for art is one of the hardest things to do, because all the shadows have to correspond in size and direction based on the location of the sun in the picture, a very tough concept to master.
It is good for kids to get outside and learn so I commend you for taking advantage of that when you can.