"Could it truly be important for children to have long, light, whimsical, colorful, imaginative, heart-wrenching books full of wonder, simply written by a Christian, even if the content is not overtly Christian?"

Yes. Think of C.S. Lewis (who wrote The Screwtape Letters and Mere Christianity for adults) also writing The Chronicles of Narnia . The Christian themes are clear, but the books are primarily fantasy stories about light, wonder, and adventure. He used the genre to bypass intellectual walls and appeal directly to the heart and imagination.

The books that shape the moral and imaginative landscape of a culture are rarely Sunday school curriculum. They are the stories woven into the cultural fabric—like The Wind in the Willows , Peter Pan , or The Secret Garden .