Is it permissible to use inherited gold—which the mother bequeathed to her daughters and its value does not exceed 4000—for the marriage of the male children instead of distributing it as inheritance, knowing that their financial situation is below average?

The mother's will is not valid because the two daughters are heirs, and there is no will for an heir. The inheritance must be divided among the children, with the male receiving the share of two females, after those with prescribed shares have taken their portions, if any exist. Whatever each heir receives in this manner is their property to dispose of as they wish, Islamically, including using it for marriage.