[Avodah] Kaddish Yasom

[Cantor Wolberg]

On a related topic, a good friend of mine, an O. musmach lost his  
father and there were many O. rabbis at the levaya.
He was told (contrary to what many feel is proper) that it was not  
kovodik for a son to shovel earth, so he refrained from
what he thought was correct. Up until he told me that, I always  
encouraged children to participate in the mitzvah. Has
anyone ever heard of this minhag or halacha?
ri