Since we really don't know much about what Lucius is like as a father in canon, it's even more speculative what he's like as a grandfather.

Personally, I think Lucius will have changed even less than his son after the war. Having narrowly escaped going to Azkaban with the other Death Eaters (according to Jo), he probably no longer says things like "Mudblood" out loud, and he and his wife have learned their lesson about putting all their fortunes behind a megalomaniacal psychopath, but I doubt he's truly repented and seen the error of his ways. So the big question is, how much has Draco reformed, and how hard does he try to keep Scorpius from being influenced by Lucius?

Since family is so important to the Malfoys, I suspect Draco would not try to keep his father away from his son. At the same time, he'd probably make it clear that he doesn't want Scorpius going off to school and spending all his years at Hogwarts in blood-feuds with Gryffindors. So I see Lucius as being quiet and restrained around his grandson, showing affection only in brief flashes, and mostly trying to earn his grandson's respect by buying him expensive gifts and showing off his magic. (And maybe slipping in a pointed comment here and there about house-elves or Muggles, just to work on Scorpius a little bit without directly challenging Draco.)