Question:
I am in the year of Aveilus for my mother, my Father's Z"L yortziet is coming up when I daven before the amud and say Kaddish do I say Kaddish for both of my parents or better to say Kaddish for my father and appoint someone else to say the Kaddish for my mother.
Answer:
You should say the kaddish, better than hiring someone else to say it. This is because when a child says kaddish for the parent it is a bigger zechus for your parent, because thier child is being mekadesh shem shomayim in public. When a child says kaddish even for both parents at the same time it goes for both of them, similar to he idea of "ner l'echad ner l'meah" , a candle lights up for one person the same as for a hundred. Therefore daven and say the kaddeishim regular.
Sources:
Be'er Hetiv O:CH 132-5 quoting Knesses Yecheskel, Birkas Reuven Shlomo 5-67. As a side point his would not apply to a person being paid to say kaddish and thyen has to say kaddish for a parent.