Is it permissible to use my mother's money—she having lost her legal capacity and I being her guardian—to give to my newly married children, or to spend on life's necessities such as food and the like, knowing that she used to do so when she had her legal capacity, and that she eats from what I eat?

The guardian of the mother's wealth is obligated to preserve it from spoilage and loss, and to develop it. It is permissible to spend from her wealth on her, in a reasonable manner. It is also permissible to mix her expenses with the household expenses if distinguishing them is difficult, provided that this is not done in a way that causes corruption. It is not permissible for the guardian to gift anything from the mother's wealth to her children or others, nor to spend it for their benefit.