Luggage
If your BP will fit on your lap, you should be ok otherwise they do enforce their baggage restrictions as they are not a shuttle service per se.

Shuttles
Check into them

Maui Bus
You will have to transfer 1-2 times most likely at Kaahumanu Center and or Maalaea Harbor

Rental Car
Check into them
You could rent a car one way to the West Side

Taxis
Share a cab with people going to the same area
Taxi service is easy at baggage claim