What is the ruling on a husband spending on his children from usurious money? Does sin befall the wife for accepting this spending? Does divine punishment in the children result from this? And what is to be done to avoid sin?

There is no blame upon the wife and children for benefiting from the husband's money for expenses, even if it comes from usurious gains, as long as the husband's work is permissible; because the sin is tied to his own accountability. The wife must advise her husband to abandon usurious dealings and to seek what is lawful.