Sorry but the whole image is out of focus. It appears that you were shooting from a higher vantage point than your subjects. IMO it would have been better if you were closer to their level. I do think the idea behind the shot is really good, just a little more work on the technicals and you will have a great image.
Quick grabshot /snapshot. Not saying that's necessarily bad but in terms of stock it should be in focus and show just what you need to show. The two girls in the foreground add nothing at all.
Too blurry. No hint of composition, looks like a quick snapshot... If this pic was composed a little bit better (not cutting off the legs of the bottom two people) and not blurred, it would work better meeting the challenge.
The subjects can move, but you should hold your camera still - this is really blurry (even the grass and non-moving objects). The hedges really draw attention to the horizon being tilted. The girls' feet not being in the picture feels strange.
More movement that has purpose would have been better. A little higher shutter speed and tracking the action in the background with a little tighter shot would have helped this a lot.