Take the bus from your resort to the Magic Kingdom.
Walk toward the MK entrance, but instead of turning right to the Entrance Plaza, look to your left. There will be three boat docks - one for the TTC ferry, one for Fort Wilderness/Wilderness Lodge, one for Polynesian/Grand Floridian. Go to the WL/FW dock, and board the boat, when it comes.
When I worked out the timing for a friend a few years ago, I came up with between 68 and 78 minutes (allowing for waiting for the CBR bus, picking up at the other stops if necessary, waiting for the launch, stopping at WL first - and walking from one mode of transportation to another, and then to Pioneer Hall). It's been a while, so I don't remember the
exact time.
He later told me my timing was pretty darned accurate
And, as indicated above, if you go to the 7:15 or 9:30 show, there will be resort-bound buses waiting right by Pioneer Hall, and Cast Members directing Guests to the right bus.