Do previous charities suffice for the remaining unlawful money, and will the donated amount (700 Riyals) after the person's death suffice for the unlawful money, knowing that the benefited amount was (450 Riyals)?

The way to dispose of ill-gotten wealth is to spend it on general Muslim welfare projects or to give it to the poor and needy. The one who does so will be rewarded for repentance, not as a giver of charity. As for an unlawful loan, it is obligatory to return its equivalent. The lender has no concern with what the borrower did with the money, and he is not entitled to demand more than the principal, otherwise, it would be prohibited usury (riba). The amount donated to the children of the deceased friend is considered charity and has no relation to the loan amount, nor does it negate the obligation to dispose of the ill-gotten wealth.