Bookpossum:
Lord of the Flies jolly? Goodness!

I hate to think what that means about the other two (which I haven't read).
While throwing names into the ring: Stephen King wrote
The Eyes of the Dragon which is styled as a fairytale and so conceivably for children (but regrettably only so so to read). Terry Pratchett has written a number of books for children or younger readers, any of which I'd happily vote for but probably won't nominate. Neil Gaiman has written a few that probably fit into this category, but the clubs have already done two of his books.
I'd be interested to see what I made of any Enid Blyton stories now - since I haven't even looked at one for a VERY long time. What do we think of Noddy, Bigears and Golliwog now? It's almost frightening.
C.S. Lewis's
The Lion the Witch and the Wardrobe I think might spark some conversation. An interesting man is C.S. Lewis.
Or maybe we might try
The Silver Brumby by Elyne Mitchell. Oh, my childhood beckons. Sadly, the works of Joseph E. Chipperfield don't appear to have made it into ebooks yet. But many of the books by Mary Grant Bruce are available very cheaply, for a little bit of children's story Australiana-style.