I'm assuming park opening is at 9? If you are fine with being in somewhat of a hurry, it should be ok. We had an 8am ADR on a 9am park opening and I think finished up around 8:45. However, we were the first table the characters visited so I don't know if that matters at all. While MK usually opens 15 minutes or so before the official opening time, there are additional ropes at the entrance to each land that don't get taken down until 9. So unless your really hurry through breakfast, you likely will not be first at the rope for whatever land you want to go to. You might actually be quite a ways back. However, you will still be in better shape than someone arriving after park opening.