As PPs have said, it's pretty easy to walk from IG to Fantasia Mini-Golf. It's about 0.8 miles (1,450 yards) from IG to Fantasia Mini-Golf (when going via the Boardwalk). You'll have to cross Epcot Resorts Blvd near the Swan/Dolphin (there is no stop light there, but there is a pedestrian cross walk).
(For reference, a walk around World Showcase is about 1.2 miles.)