I can't find examples of gravestones (matsevot) with both parents' names in Hebrew. For a kohen, the options seem to be
Ploni ben Almoni ha-kohen v'Almonit
which I don't especially like, as it makes the mother sound like kind of an afterthought;
Ploni, ben Almoni v'Almonit, ha-kohen
which I like, but the two commas are crucial, otherwise it seems to be saying that the mother is a kohen; or
Ploni ben Almonit v'Almoni ha-kohen
which is syntactically correct but a bit odd, as we generally don't put the mother's name first.
Is there an accepted right way? Are there sources or examples (I can't imagine any earlier than the 20th century)? Are there other better options?