If you want to make your reservation for earlier I would suggest using a cab. Even if you went to the MK, what you find in the mornings that the buses that are dropping people off for the park openings are not going back to those resorts. You'd need to get there early and check with the bus driver to see if he is going back to the AKL.
The reason I mention this, is that it happened to me, I was going to get on the bus that had dropped people off from the AKL but the driver was being dispatched back to another resort.
I found that I had better luck with a later reservation at Boma, and actually going to the early entry park (if there is one that day) and then getting the AKL bus from that park.