Read the story of Jonah and the Whale to the children. You can choose to read it directly from your Holy Book, or read a children's version in a children's Bible or a book like "Jonah and the Whale" by Sophie Piper or "The Whale and Jonah" by Deedra Scherm.
Ask the children questions about what you have read. How would they feel if they were Jonah? What do they think is God's lesson in the story? Why is this story told? How did Jonah feel when he was inside the whale? What was Jonah afraid of?
Have the students act out the story, using a few of them to play the main characters for the class. You can make a script together or you can have the students improvise to get a feel for how well they understand the story.
Ask the class to draw a picture of how they interpret Jonah and the Whale. Have each child stand up and discuss his picture and what he drew. Hang them around the classroom when they have finished.