One of my favorite children's books to read to the boys is There Was an Old Man Who Painted the Sky, by Teri Sloat (Author) and Stefano Vitale (Illustrator).
It tells of a young girl discovering the ancient cave paintings in Altamira, Spain, with her wonder framed by the six-day Genesis creation story. She expresses her amazement at how the Old Man above it all created everything, as "it's up so high."
The book uses the idea of God as an artist, who paints the cosmos into creation (Tolkien has the similar idea of Creation sung into existence by God and the angels in The Simarillion). God then gives creation its own proper freedom to paint and create, which leads to the cave's existence and the child's astonishment.
Without being pedantic or conceptual (which don't work well with children, anyway), the book conveys the wonder of existence, beauty, creation, and transcendence. It's a pleasure to read, especially in its evocation of a Biblical sense of amazement at the world and God.