There is no direct bus. They could go to any park and then take the bus to WL. The bus ride from MK to WL is only 5 minutes - or they could take the boat from MK to WL - it takes a little longer but is a nice ride.
What Kristi said is right. Take a bus to the nearest park, EPCOT in their case, and then take a bus to WL. You should be able to pick up a WL bus at DTD also.
We were at POR last September, and visited Wilderness Lodge for a meal. We took a bus to Magic Kingdom, then the boat to Wilderness Lodge. It was such a lovely ride, relaxing and gorgeous views!