Melvin probably wouldn't be the best place to take a beginner fly fishing...with the conditions at this time of the year being a little tempermental and the trout not being that easy to catch at the best of times!
Rather than the 2hr trip to Melvin I suggest that you get your dad up to the likes of Moorbrook to develop his casting skills and catch a couple of stockies...then when he has grasped the technique take him the the wild western loughs of Ireland
Or
Take him to Melvin and teach him how to row a boat in a big wave so YOU can nurse the Garrsion shore for a big Roo or silver boy (probably more red than silver now though!)
Tight lines anyway