I should like to take this opportunity to thank everyone who has replied with thoughts on my post regarding religious stories. I now have a wealth of ideas and offers of stories - thank you.
What only now strikes me is that I forgot to mention that it is my intention to reformulate these stories as children's stories, which of course puts some limits on what material I can use. In particular it does mean that I am looking for relatively pithy, standalone, parable-like stories. As an example, Sharada Chandrasekar suggested the Mahabharata; however I've looked at the dialogue between Krishna and Arjuna in the Bhagavad Gita, and find I'm hopelessly overwhelmed. I don't know the script at all well enough to pick out a section which could be used as the basis of a standalone parable. This is where it would be really helpful if people could send me references to concrete passages which I could use, or else links where I can find the relevant passages online.