The answer depends on if you're going to WCC for breakfast or for dinner.
If breakfast, you definitely want to take the larger boat from MK, not the smaller launch from the Contemporary. In the morning, the latter goes from the CR to Ft Wilderness and then to the Lodge, so you'd be going way out of your way. (A very pleasant ride, though.) If it isn't really early, you might take the launch from the Poly straight to the MK. It's a nice ride across the lagoon, but I don't believe the launch starts running as early as does the monorail.
If dinner, take the monorail to the CR, go out the back door to the boat dock, and take the launch to the WL via a fairly short ride. (The launch changes directions in the afternoon and goes CR-WL-FtW.)
To reply directly to B-Ride, there are two separate boat routes to/from WL, with no boat running between MK and CR.