Is this sentence correct:
,, Children's magazine is something which children usually read.'' ?

It isn't

The correct spelling should be Childrens'

the symbol of the grandfather's heritage in this excerpt from "the medicine bag,” is the beaded bolo tie.

a bolo tie is a cord fastened around the neck with an ornamental clasp which is worn as a necktie. they have been used by native american tribes such as hopi, navajo, zuni, and puebloans since the mid-20th century.

therefore, the fact that the grandfather is wearing a bolo tie refers to his heritage as native american.