As for the picture, my first thought was to crop it tighter. The attention should be on the kids, and the cars and tree in the background distracted me a bit. You could try cropping the top so that only the bottom of the cars is showing.
I really like this picture. I agree with the above, crop it so that the children are at the very edge of the picture, maybe even some of the area over the cars. Otherwise, I think this is a very nice and entertaining shot. A great catch!