Beautiful kids...not a studio portriat though. Since you chopped off a portion of the boys foot, it would look better if you cropped off about all the way to his knees.
Would be a great pic if they were in some light. The shadow makes them hard to see. Maybe some reflected light on to their faces would have been good.
Otherwise it has potential of a great pic.
cute kids, but looks like a backyard shot. Take that pose and move them indoors and give them some decent lighting and it would work for the challenge.
The part sun, part shade I think created some exposure problems, just too contrasty to get a good capture, perhaps fill flash would have helped, or moving your subjects completely out of the sun