There are no direct buses from any of the parks to DTD. They do this so that people won't try to take advantage of the free parking at DTD, and then go to a park to avoid the parking charge.
There are two different options. You'd have to take a bus from AK to a resort (such as AKL) and then take another bus to DTD. Or take a taxi from AK to DTD, which is quicker than the two-bus option.