Opinion and advice on picture for photo contest???

I agree, the first one is probably the best. I also like the turtles, but I don't think it's winning material, you weren't quite close enough, and the light and exposure isn't as good as the first dog. If you want to use your dog as the model, I would keep trying. After all, you have several more weeks. I'd rather see the dog's ears included in the composition. I think if you keep at it, you may get one that's even better than the images you have posted. Good luck!