Captin Cooks does serve Tonga Toast but just be aware that it can very busy in the morning! We don't like eating inside, but love grabbing a pool side table; the lagoon area is so nice in the morning!
I'd take a bus to the MK and catch the monorail over. Captain Cooks is located in the Grand Ceremonial House, 1st floor, by the pool. It's quick service so you shouldn't have a problem waiting etc.
If your going back to the MK, you can then walk to the TTC and catch the express monorail/ferry back, catch a boat from the resort boat dock (will stop at GF then MK), or just finish riding the resort monorail through the GF! If not, just catch a bus from the resort bus stop or walk over to the TTC and catch the monorail to Epcot.