I would call the WL and ask about the specific dates in which you are interested. In general, I believe that transportation begins between 30 minutes to 1 hour before the park opens, depending on expected crowds. But don't quote me!
We had a 8:05 ps at CP. We took the 7:30(earliest) boat to the Contemp. We were going to walk over. But the Captain offered to boat us over! We got there by 10 til. I think you could take the resort boat and walk over as we had planned.