Just as your pops goes to the dr to check on what to do about his health and how to deal with his abilitys due the same with pet~
take him to your vet and ask him just the way you have asked us~ He,ll check him out and give you the Best advice.. if All seems Good for both of them Maybe you ,dad & dog could all 3 make it Short but Sweet and Show YOU CARE ABOUT BOTH of them ~

yes you should start running with him its never too late, you should start with short distances, you wouldn’t want to push too hard too fast, i guess start with a couple blocks

Well, unless you want a workout in the possess, I’d say it’s probably better to let him run around by himself – supervised, of course. My dog is a bit older then seven now, and I’ve noticed that he’s been winding down. When I let him off his line to run around, he usually sniffs around and eats grass instead. He does some frolicking, but not like he used to.

If you run with your dog, he’ll feel the need to run also and keep up with you. He may push himself, and at his age I wouldn’t really recommend that.

Is it possible to let him off his line? If he can take things at his own pace, it’s much better.