Is it permissible to invest money of a questionable source, resulting from usurious transactions, for the benefit of grandchildren without the knowledge of their parents?

Borrowing with interest from usurious banks is unlawful (haram (definition)), and dealing in cigarettes, whether by selling or buying, is unlawful (haram). Whoever does so, knowing of its unlawfulness, must repent. Any profit resulting from usury or the sale of unlawful items must be disposed of by spending it on charitable causes. There is no sin upon one who did so before knowing of its unlawfulness, but they must dispose of the profits resulting from unlawful transactions by spending them on general Muslim welfare or for the poor and needy.