The transportation folk at Disney are pretty good at getting you to your early morning ADR's, well in my experience. We've been able to get buses in plenty of time for breakfast's at parks also. I've had 8:05 am reservations at AK and MK and been able to get resort buses (check with concierge/front desk for times) Same goes for the monorails, been able to get to MK and Contemporary for those early morning times.