If magic kingdom is open, you can take a boat or bus to WL. There is a boat between Contemporary and WL. But it doesn’t start running until late afternoon. I believe it also stops at Fort Wilderness.
I believe that the boat starts running now at 3:00 pm? You can always check at the CR guest services, to be sure of the schedule.
From the CR to WL before 3:00pm (or prior to the direct boat) walk to the MK bus stop and take the bus OR walk a bit further to the MK -WL boat launch and take the boat. After 3:00 pm, take the boat directly from the CR to either Fort Wilderness or WL.
From the Poly or GF take the monorail or boat to the MK. Then go to the boat launch to WL or walk a bit further to the MK bus stop and take the bus to the WL.
these work while the MK is open and has transportation running. If you are travelling later into the wee hours, you may need to take a bus to/from Disney Springs, if it is open later. Or call an Uber/Lyft.
ETA:
OK, just read that you are using an
ECV. Some boats will not accommodate an ECV, especially from the Poly and GF to MK., So I recommend that you take the monorail and bus from Poly or GF. From CR, just walk to the MK bus stop and take the bus from there.
Otherwise, you may be waiting for a second boat which can take an unnecessarily long time.