Buses start running, from resorts to parks, by 6:30am. They don't come quite as frequently as the regular park buses, so you need to leave plenty of time to get to your ADR or tour.
For instance..you have an 8:05 seating at MK...be out at the MK bus stop, at your resort, by 7am. That way, if you just miss the bus to MK, you may have a wait of up to 20 or so mins before the next one comes. Then add in the 15 min ride to MK, and you have already taken close to 40 mins. It will take you another 15 or so to get from the bus to the restaurant. I imagine it will be either Crystal Palace or CRT.
There are these early buses to all parks. There are no buses, from resorts, to the TTC.