I gave this a higher mark than I normally would due to the potential for this to be a very good shot with just a couple of small tweaks, especially cropping. The problem with all impromptu shots is that they *are* in the spur of the moment, and thus don't always fit into the nice, neat boxes of "form" and "composition" that we might prefer to see. For me, as much as I enjoy all the benefits of digital photography, the one thing that I dislike so much about it is that it is so easy to correct minor flaws that we expect every shot to be perfect. Sometimes a little imperfection makes for a better photograph, and I felt that this was one such case. Crop it as a vertical image, which will eliminate 80% of the overlit background, and I think you've got a shot that you'll be pleased to blow up to 8x10 and hang on a wall.
What a sweet image. I vove how the child is playing and the dog is sitting at attention. With that said, this image has some issues with oversaturation and lighting (the childs face could use more directed light). A closer crop on the dog and child would probably help as well.