I like the photo-journalistic quality of this. The detachment of the boys from the bike seems to say a lot about their every day world. More contrast and sharper focus would make this a bit better.
I don't feel that wheel is the main theme here. With that old bike, you might want to try some close ups of just sections of the wheels. The rusted metal, combined with chrome could give the picture some awesome texture.
I think the flash attached to the camera was the worst invention in camera technology. It guarantees flat lighting, and glare from shiny backgrounds. This would have been a really interesting shot with natural lighting, even if it would up with blurred motion. Disable your flash, and take more pictures!
Maybe it would of been best to focus on the bike. I think your trying to put too much into one photo. You could of had one of the boys stand by the bike? This way you clipped off the front tire and the boys looks squeezed in. The shine on the plastic makes it hard to control bouncing lights/flash.