|There's a lot of potential in this picture, but I think it needs some more work to bring it out. The subjects are very sweet, and you have captured a great moment. A couple of things though. The girl's face is cutoff at the ear, and that is very distracting. Also the focus is not sharp enough, the light is bland. A little work in PS with curves, and some dodging of the eyes can help with this. Also with the composition as it is, the eye flits back and forth between the children and finally settles on the background, which incidentally seems to be pretty well focused.
You have photogenic subjects, though, esp. the little girl. You could probably get a stunning shot of just her with some good light and sharp focusing on the eyes.