Is it permissible for a wife to take money from her husband, who is addicted to drugs, without his knowledge, on the grounds that her children have a greater right to this money than for it to be spent on drugs?

The default rule is that a wife is not permitted to dispose of her husband's property without his permission. However, if the husband withholds her right or the right of their children to maintenance (nafaqah), then it is permissible for her to take from his property what is sufficient for their needs, according to what is customary, based on the hadith of Hind bint Utbah. If what she takes is for essential maintenance without extravagance, then there is no blame. But anything in excess of their needs and without the husband's permission is not permissible to take.