Years ago, I came up with a cute idea:
Poqeid Avon Avot al Banim refers to visiting the sins of the parents through, or by means of, the children. This constitutes a serious warning, "Honour your father and your mother, lest you be punished though your children."
- Rabbi S.R. Hirsch, new edition, p. 243 on Bereishit: 9:24
Rabbi S.R. Hirsch applies this to Noah's curse of Ham. Sins that children commit against their parents will be punished by the manner in which their own children, in turn, will deal with them. K'na'an's actions would be the mechanism through which Ham's dishonour of his father Noah would be punished.
This is my own P'shat on Poqeid Avon Avot al Banim. Baruch Shekivanti!