Yep, to get to Mickey's Back Yard Barbecue, the best thing is to get a bus to Magic Kingdom, then a boat to Ft. Wilderness, then its a short stroll over to the barbecue.
However, the best advice I can give you is not to think about getting to dinner locations from your resort. There is rarely any need (or time) to go back to your resort to "dress" for dinner.
If you want to go to the Barbecue one evening, or any of the monorail resorts, or Wilderness Lodge, then plan to be at Magic Kingdom that afternoon.
If you have a dinner at one of the Epcot resorts, then plan to be at Epcot or the Studios that afternoon.
If you are eating at Saratoga Springs, OKW, Port Orleans, plan to be at DTD that afternoon.
If you are eating at Animal Kingdom Lodge, plan to be at Animal Kingdom that afternoon.
Also, try and plan those resort dinners when the nearby park has Evening extra magic hours, so you have a nearby park still open to get back to your resort without going to DTD.