You can take the resort monorail to MK starting at about 7:15. For AK take a bus, which will start running through the Poly an hour before AK opens.
BTW, just because you arrive at a park early, it doesn't mean you get in early. The parks are opening the turnstiles at official park opening time nowdays, or sometimes a few minutes earlier if there is a large crowd. They no longer open Main Street a half hour early at MK except on extremely crowded holiday weekends. So the best you can do is be at the head of the line at the turnstiles...... and wait.