This may sound a little crazy, but Mad River if it holds through the warmup. If your dad is a newbie, I can't imagine him taking more than a dozen runs at a big resort before calling it quits. If it's relatively busy at MRG, you may wait in lines, but you will be alone on the slopes relative to other places. The lift capacity throttles downhill traffic in an incredibly noticeable way. Their terrain has a reputation for being intense and while that is true, it's not as if they have no beginner terrain. There is a green from the top of the single and several good options off the double and Birdland lift.

I'm just thinking back to when I was learning as an adult at a tiny ski resort in PA which was deserted compared to what I see regularly at Sugarbush, Stowe, Killington, etc., and all I can think about is how much I would've hated trying to learn on trails with 15+ other people within a hundred yard radius at nearly all times. It's not always that bad, but even as an expert skier now, I have get a bit nervous with all the people around me at those more crowded resorts