My Alimony had over two hundred races, then went on to be a broodie. She's now eight years old, and is the picture of health and vitality. And she is a nut. She runs circles around my five year old girlie who had a career half as long, and no puppies.
I would say any of your three options sound fine to me. Any dog can have health issues regardless of age. Yes, the odds of something happening generally increase with age, but honestly, I'd probably choose the older pup.