Contrary to popular belief, there is no real fixed set order. It all depends on time of day, demand, and things going on.
Typically speaking though, this is the usual order for morning pickup. (8am-11am)
Swan -> Dolphin -> Boardwalk
Yacht -> Beach -> Boardwalk
Because both buses service the Boardwalk, you may see two of the same bus arriving at the same time. If a bus fills up, and doesn't make all 3 of the stops, then the Dispatcher has the option of sending out another bus to continue where the first bus left off. The Dispatcher also has the ability to have that extra bus run backwards. (ie: Boardwalk -> Yacht -> Beach, or Boardwalk -> Dolphin -> Swan)
During non-peak afternoon times, or at slower destinations (ie: AK & DTD), the post 11am buses will run with all 5 resorts.
Swan -> Dolphin -> Yacht -> Beach -> Boardwalk
9 times out of 10, this is NOT a problem. The rare case that a bus does fill up, another one can be sent in.
Contrary to popular belief, it does not take that long to make all the stops.