No one has mentioned the connection between this image and the usual meaning of the Sun. Here's a quote from the typical RW meaning:"...coming out from the walled garden of the sensitive life...the transit from the manifest light of this world, represented by the glorious sun of earth, to the light of the world to come, which goes before aspiration and is typified by the heart of a child." Thus, we have a connection between the life-giving light of the Sun and the vitality and life of children, also the clear true sight, wisdom and optimism of the Sun and that of children, etc.
As usual, the Bohemian-Gothic does a wonderful job of putting a twisted spin on this card. In the typical RW image, the child on the white pony waves a red banner--here he wears red, which we know is a dangerous color in this deck
And the garden of "life" is dark and barren. His expression isn't innocent so much as naughty. The movie "The Innocents" comes to mind--from the Henry James novel "The Turn of the Screw." Also the "Bad Seed." Stories of innocent children who are not so innocent, and/or adults who are led to bad ends by putting too much faith in childhood innocence. Where will this particular child on the pony lead us?
Logic, reason, optimism, innocence are good things for fighting the darkness; sunlight, after all, kills vampires and sends ghosts and such back to their graves. But we also know very well that the character who says, "Pish-posh! There's no such thing as _________" is going to die quickly from the very thing he/she is dismissing as nonsense. We also know that the path to hell is lined with good intentions and that we can as easily be blinded by too much light as enlightened by it. Hence, this card tells us that too much reliance on light and reason can trap and imperil us. Looking only at the beautiful child in the light means we miss seeing what might be hidden in the shadows or the fact that he came from a barren garden. You can't defeat the darkness by ignoring it's existence.