Siobhan,
thank you for sharing this lesson outline adapted to your own context. For teachers who don’t have a whiteboard with a low enough light to be able to block it, you can put object on meter sticks or poles, or find an unused projector that you can mount lower down.
You might consider making a shadow theatre set up. In this way, the children behind the stage create a show that can be viewed easily, without their own shadows blocking.
Here is a make your own: https://www.hallmarkchannel.com/home-and-family/how-to/diy-shadow-puppet-theater