Is there any doubt concerning the money of a deceased son who worked in a bank, and is it permissible to give charity on his behalf from this money?

If your son's heirs know that his wealth is unlawful or contains a proportion of unlawfulness, then his wealth should be examined: If it resulted from a permissible act, then it is a permissible inheritance for his heirs. If it resulted from an unlawful act, it must be disposed of by spending it on the welfare of Muslims. Similarly, if it is mixed, the unlawful portion should be removed, even if by estimation. If its source is unknown, then it is permissible. As for what was permissible, the heirs may give charity from it on behalf of the deceased, but the consent of the other heirs is required if the deceased has heirs other than yourself.