Can you post a picture of her body from above? From those pics, it looks like she can afford to lose some weight. It's best for a dog not to be carrying around extra weight on their joints. Here is a good guide:
We walk everyday and go to the park on Saturday and Sunday mornings. Would going to the park and chasing a tennis ball everyday be a good way to ramp up her exercise our do you think it would be too much on her joints?