No buses between DTD and the parks.
Yes, going to All Star and transfering to the DTD bus would be just fine as All Star is just about 3 minutes from AK.
You could also go to any resort that is closer to DTD and transfer to the DTD bus.
You could choose to take the bus to the new Saratoga Springs Resort & Spa which is within walking/boat-ride distance from DTD.
The bus to the resort will take anywhere from 3 minutes to 20 minutes, then the bus ride from that resort to DTD will take another 10 to 20 minutes depending on which resort you used as a transfer point.
Allow time to WAIT for a bus at both stops.