Halakhah sur Malachie 1:6

Even though the saying of kaddish and prayers are helpful to [the souls of] the parents, yet they are not the main thing. The most important thing is that the children walk in the path of righteousness, because with that they gain Heavenly favor for their parents. Thus it is written in the holy Zohar: (at the end of the portion Bechukosai) "A son honors his father."¹³Malachi 1:6. This statement is similar to the Divine command "Honor your father and your mother,"¹⁴Exodus 20:12. which teaches [that a son must provide his parents] with food and drink. All this he must do while they are alive. but after their death you might think he is exempt, this is not so. Even after their death it is his duty to honor them even more, for it is written, "Honor your father;" and if the son walks in the path of evil, he surely shows contempt for his father, and disgraces him. But if the son walks in the path of righteousness and acts properly, he certainly honors his father thereby; he honors him in this world in the [eyes] of men, and confers glory on him in the other world in the presence of the Holy One, blessed is He. And the Holy One, blessed is He, has mercy on him and seats him on His Throne of Honor … (end of Zohar text). A person should, therefore, instruct his children to observe one certain mitzvah [with particular care]. If they fulfill [this mitzvah] it counts for more than saying the kaddish. This is also a good course [to follow] for a person who has no sons, only daughters.