Welcome to Yorkie Talk and congratulations on the new addition to your family.
I am an Oscar and Angus fan too.
My family had an Airedale whom we adopted as an adult -- coincidentally, she was 85 pounds and 6 years old. She was very well trained and sweet as can be, but not socialized with small dogs. We could not trust her with small dogs. (ETA: this was years ago, long before we had our Yorkies)
Wanda gave great advice to supervise closely -- and do lots of training.