We have added a puppy to our house quite seamlessly. Our old lady, Wink, is her cuddle partner and Birdie her playmate,teacher and disciplinarian.
http://forum.greytal..._1#entry4860278
Smokey was just about 3 months old when she came home.
The way you describe your grey's personality sounds a lot like my hounds. They lived with cats as well but we don't have cats now. She should do just fine with a puppy. Supervision and a crate are key!
Good luck with your search.