[Sherman Logan]

My personal vote goes for Tolkien. No overt preaching like Lewis, but IMO much more effective for that very reason.

[AnAmericanMother]

"The Hobbit", "Smith of Wooton Major" and "Farmer Giles of Ham" are suitable for young'uns - LOTR is a little heavy going unless you're an exceptionally well-read middle schooler.

It doesn't seem to me that Lewis overtly "preaches" in his children's books (of course he does in his apologetics, and to a degree in "That Hideous Strength") - can you cite some examples? At least it's not obvious to kids. When (at age 7 or so) I read at the end of The Last Battle "then he no longer looked to them like a Lion," I was very surprised!