Based on the course map they should in theory be able to watch/cheer at the finish area since it appears to be in the same spot in the Epcot parking lot as the other half/fulls. Or, they should be able to watch/cheer over at the Yacht/Beach club walkway around mile 11 1/2-12 before the runners enter Epcot.
Watching from near the finish line may be the easiest as they should then be able to hop on the shuttle buses. Watching from the Yacht/Beach club would require a cab, or transfering buses at DTD (unless you are staying at an Epcot resort).