Not sure why you'd want to come in a bus from DtD to Fort Wilderness. If you're already in a car at DtD, I'd just drive on to FW from there.
Also, the Campfire Singalong is not in Wilderness Lodge, but at Fort Wilderness, a totally separate Disney resort.
If you must take a bus to FW, you'll probably have to get off at the front of the resort, and there are internal buses which will take you to where the singalong takes place.
Another option is to get to MK or Wilderness Lodge, in whatever way possible for you, and then take a boat from there to FW, where the dock is on the other side of the resort from the bus stop, and possibly a quicker walk to the singalong.