I like that you're venturing into portraits too. And doing them in natural light has its challenges especially out in the open when fighting harsh lighting conditions. Good on you for finding shade for the boy and trying to control your light.
However letting the background get brighter than the subject pulls it forward while forcing him back.... it basically makes the image appear rather flat.
Dean Collins (wrote the book on sculpting with light) stressed 3 things that affect dimensionality: density, contrast and saturation. Brighter, more contrasty and colourful items appear closer than those that are dimmer, more faded and less detailed.