You sound like a wonderful mom. I am a huge believer in long walks. My little girl, Katie, is seven, and we walk daily, often three miles at a time, sometimes more. We also play a lot, and I know the exercise keeps her healthier. My last Yorkie, Ashley, walked daily, usually about two miles or more a day, up until a week before she passed away close to her seventeenth birthday. My vet could not believe how strong her heart and lungs were for a dog her age and also how fast she was.
I read something that was posted on YT by a dear friend of mine who knows a great deal about movement and exercise. It is from Puppy Culture, and it wrote how much exercise a puppy should have at each stage of their life. The author raises bull terriers whose growth plates close much later than a Yorkie's growth plates at approximately eighth months. It's a really interesting article, but I thought you'd find the quote below relevant.
https://www.puppyculture.com/tablet/...-exercise.html
"Probably the biggest cause of growth plate and soft tissue injury is repetitive exercise with a young puppy. So, until he’s about 18 months old, long hikes and walks are out and lots of free-play sessions are in."