The perfect companion book for the study of John for kids is Miracle Man: The Story of Jesus by John Hendrix. Beautiful, full-page illustrations tell the stories of Jesus’ life leading up to and including the cross with his resurrection the last page.
Jesus is depicted historically accurate as well as the buildings and the clothes. He is also drawn larger than those around him, which I love and my kids noticed right away. It makes him stand out and emphasizes the point that he is greater than us.
Nice summary of the main stories in John and elsewhere. A quick read. Highly recommended.