The story of Cain and Abel is a window of opportunity to discuss issues that are close to the hearts and minds of preschoolers. It is a story about jealousy, anger, fear, and morality.
When telling this story, I try to gravitate away from the murder and focus the discussion on one of the following topics:
God preferred Abel's offerings and that hurt Cain's feelings. How do you feel when someone rejects your present?
We are told that God favored Abel's offering because it was from his heart and he chose the best sheep, whereas Cain who did not choose the best of his crop. I talk to the children about the importance of giving and the difference between giving a broken toy or a toy that we love and have a difficult time giving up. A true act of kindness is in giving up something that you cherish rather than something that you no longer need.
This story is about law and order. God establishes the rules of the land. If the rules are broken then you will be punished. Later on, the Ten Commandments reinforce these laws, e.g. 'Thou Shall Not Kill' is a clear reflection of a commandment arising from the Cain and Abel story. If you feel this is a topic that will touch your children and will contribute to their development, then I would suggest discussing the importance of rules in the home, the classroom, the road etc. You can also discuss the Ten Commandments and how rules are enforced in order for our society to function efficiently.
Check out this Good Fruit Bad Fruit Mobile as a follow up activity for this story