When Murray and I got certified last winter, Bruce, a 10 year old boxer who lives in the mountains in the center of the state, was certified at the same time. He and his owner are the only team in their area, and they are overwhelmed with requests.
He is a sweet, white-faced old boy (the dog, not the owner

). I think the old folks he visits appreciate his stiffness and difficulty in getting around at times, and have a special bond with him because of his age. He loves the patients he visits,this helps keep him active, and he is a real star in our organization.
As long as the dog enjoys what he's doing,and is physically able to do it, age is not a limitation!
I hope Lady gets a good report at the vet, and that you can figure out what will work with her as far as food- good luck!