Catherine,
have you a particular Sun documentary you would choose?
Tracing shadows is great fun – do you have a suitable light source in your classroom and can you make the room dark enough? I have tried it inside my new classroom at Blackrock, but I have three small windows to one side that I cannot easily block, so I always have extra light sources. I have learnt to keep a big piece of cardboard to cover them up. The old room I had was a complete no-go for shadows, big windows on all sides and the blinds did nothing!
This is an activity that is best in a darkened room, or you could create a “light and dark cave” as suggested in this ESERO activity: https://esero.ie/wp-content/uploads/2015/01/09_Light-and-darkness.pdf