Funnily enough, I had the exact same dilemma over here!
My daughter (who lives in her own house) rescued a (big!) labradoodle boy, Luka....and I was quite unsure as to how to get our Harry (Yorkie, but 20lbs!!) used to him.
We did exactly as Mike suggested, took them on leash walks side by side with the 'people' in the middle and, do you know, we've never had a problem
Now when Harry sees Luka, he goes on his hind legs and kind of cuddles Luka round the neck, and Luka licks his face!
I truly hope it all works out well for you all - and I think you're very thoughtful, too! Sally + Harry x