Probably still by 6:30....they 'might' start by 6, but you would have to ask a bus driver that when you get down there. Don't ask at your resort...they have no idea! I asked at my resort....I was told that the buses start running an hour prior to opening! This was about 4 months ago....I ask every once in awhile just to see what they will say.
The bus drivers will be your best source of info. For a 7am ADR, I would be very tempted to take a cab to the CR and then walk over to the MK.