You must take an internal bus to either the Settelment - to catch boat to MK or bus to MGM, or take an internal bus to Outpost to transfer to another bus to Epcot, AK or DTD.
We stayed in the cabins and drove to the parks, with the exception of MK. We had all the kids and two strollers to lug around. I must say that the internal bus system was great.
The only time the wait gets longer is in the evenings around Hoop-Dee-Doo show times, due to higher volume of people on buses and boats going to the show.
We never had a long wait to catch a boat to MK, and we also took boat to Contmeporary for PS at Chef Mickeys.