All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.
It is established in Islamic Law that it is obligatory for a husband to provide for his wife and children. However, if the wife took the initiative to provide for her family with the intention of drawing closer to Allah, whether her husband is solvent or insolvent, then she will have a great reward from Him. This is supported by the following verse: "As to the Righteous, they will be in the midst of Gardens and Springs, Taking joy in the things which their Lord gives them, because, before then, they lived a good life. They were in the habit of sleeping but little by night, And in the hour of early dawn, they (were found) praying for Forgiveness; And in their wealth and possessions (was remembered) the right of the (needy,) him who asked, and him who (for some reason) was prevented (from asking)."{Athariat, 15-19}.
Almighty Allah has established special rulings for spending on relatives since, as well known, (giving) to a relative is two things, charity and upholding the ties of kinship. Moreover, the fact that the Prophet (PBUH) mentioned relatives first indicates that they enjoy a special status. This is supported by the following Hadith: ……… (Zainab added): So I went to the Prophet and I saw there an Ansari woman who was standing at the door (of the Prophet (PBUH) with a similar problem as mine. Bilal passed by us and we asked him, 'Ask the Prophet (PBUH) whether it is permissible for me to spend (the Zakat) on my husband and the orphans under my protection.' And we requested Bilal not to inform the Prophet (PBUH) about us. So Bilal went inside and asked the Prophet (PBUH) regarding our problem. The Prophet (PBUH) asked, "Who are those two?" Bilal replied that she was Zainab. The Prophet (PBUH) said, "Which Zainab?" Bilal said, "The wife of `Abdullah (bin Mas`ud)." The Prophet said, "Yes, (it is sufficient for her) and she will receive a double rewards (for that): One for helping relatives, and the other for giving Zakat."{Bukhari & Muslim}. In addition, it was narrated from Salman bin 'Amir that the Prophet said:
"Giving charity to a poor person is charity, and (giving) to a relative is two things, charity and upholding the ties of kinship." {Related by Nasa`i}. Since the mother isn`t Islamically required to spend on herself, her husband and her children, her doing so entitles her for a great reward from Allah.
In conclusion, if the mother intends what she spends on her husband and children as charity, then this is a great act of righteousness; for which Allah has dedicated a special reward in the form of blessings in this world and the next. And Allah the Almighty knows best.