Were Naaman and Ard the sons or the grandsons of Benjamin?

They were the sons of Benjamin

And the sons of Benjamin were Belah, and Becher, and Ashbel, Gera, and Naaman, Ehi, and Rosh, Muppim, and Huppim, and Ard. Genesis 46:21

They were the grandsons of Benjamin

And the sons of Bela were Ard and Naaman. Numbers 26:40