(newbie here --wave--)
I have a sheltie along with our new yorkie. Now my sheltie is older, he is 9, and is smaller for his breed, less than 20 pounds, but I still have to watch him not to play too rough. When they both play fetch Jasper (sheltie) will plow over Satchmo (yorkie) to get to the ball first.
Jasper has TONS of energy still and he sheds sheds sheds (I do not have dust bunnies, I have dust dinosaurs and they have to be caught and herded to the garbage daily). I think it would be easier to have the yorkie first and sheltie second, simply because Jasper is so very eager to please, but we are all dealing well here. He didn't like the new baby at first but he was NEVER selfish - he shared toys, water, food and crate without being nasty - "treats" were his only cutoff (the puppy was NOT getting his ice cube - Jasper loves ice)
The below write up is RIGHT on the money if compared to my guy. He is very vocal (if you aren't used to it, it can be annoying) and he is busy herding all the time. Jasper is no stroller dog, but he travels well and thinks that anyone who can throw a tennis ball is his bff.
Shetland Sheepdog - Wikipedia, the free encyclopedia
Good Luck with Prince and in finding a manly dog for your spouse!
Amy