That is cool!
One suggestion: you don't have to turn the background to be BW. You can reduce the color instead of change it completely to be BW. I can see you might use the BW brush in PS to process the picture. But because the hair of the dogs, it is very hard to do so. That is why I think you can simply adjust the color and contrast, the picture will still look awsome!
No matter what, the most important thing in this pic is dog's motion and due to the focus and the depth of the field, you already make it very clear.