Neither the son nor the daughter-in-law are named in the credits, just credited by their relationship to the Grump. The son does refer to his wife as Liisa (and Lissu, a term of endearment) in the English subtitles.
When Timo and Mielensäpahoittaja are cleaning the gutters at night, the Ford Escort is parked on the right-hand side of the driveway facing the house. When Liisa, has daughter-in-law, returns that night in her Audi, she must park on the left-hand side. The next morning the position of the cars is reversed.