It is pretty common for an owner of two dogs to end up with an 'accidental' litter, actually. They get a bit careless, don't get the female spayed or the male neutered... next thing you know, puppies!
I just want to point out that I have a collie that was from an Irish farm and is a dream to own, she is absolutely no trouble. She has a perfect on/off switch and isnt a chaser. I think this particular combination of breeds will give you a highly intelligent dog that will need some purpose in it's life and a good deal of exercise.