It depends. If its a morning that there is morning madness and you have passes for it, Mickey and Minnie might not be in their houses in time. They do meet and greet in the street before the ceremony. And I believe you can still walk through the houses if you want to look. Never tried it, but I'm pretty sure. If its a morning madness day (Mon, Wed, Fri and Sat) and you don't have tickets, you probably wont have time. As the area will be full of people when you arrive. If its a day the park opens at 8, with no morning madness, and you are there waiting for them to open at 9, you'll probably be fine. However, I'm not sure if Mickey and Minnie are there right at opening or not.
Thats about as clear as mud, isnt it?