Grasses for shade include Hakonechloa macra aureola and other Hakone grasses, Chasmanthium latifolium, and to some extent, Calamagrostis brachytricha.
That said, it is very difficult to grow anything under a maple because the fibrous root system sucks up all nutrients and water. I once was able to get Liriope spicata (not L. muscari) established under a silver maple. I suggest your father try that.

I have a Hakonechola macra aka Japanese Forest Grass growing under my Maple. It is about 6-8 feet from the trunk. I am in Zone 5B. Your dad may also want to try Luzula. I also understand that Karl Forester is good for dry shade.

The Karl Foerster I see around town (near Boston) is either beautifully stiff and full (in full sun) or thin, with erectile dysfunction (in shade).

All kinds of Carexes will grow in a dry shade and be pretty much contained.
In wet shade they are invasive.