Is it a mitzvah of some sort to visit the grave-sites of parents or other close relatives at the cemetery (as opposed to it being primarily sentimental/emotional in nature)? To what extent must one go out of the way to make such visits and need one feel bad about not making such visits?
Lots of different practices about this.
There is a point in coming together approximately a year after the burial to make sure the tombstone is set up properly.
Otherwise, Rabbi Moshe Feinstein was not in the habit of visiting family graves, and he said he was following the custom of the Volozhin yeshiva that way. Yet before he left Russia (and he had a feeling it was for good), he stopped to say goodbye to his father's grave.
If it works for you, fine; if not, fine. I don't think someone needs to feel guilty for not going.