Praise be to Allah.
With regard to reading Qur’aan, there is some difference of opinion among the scholars as to whether the reward from that will reach the deceased. According to the more correct of the two opinions, it does not reach them, because there is no evidence to that effect, and because the Messenger (peace and blessings of Allaah be upon him) did not do that for the Muslims who died, such as his daughters who died during his lifetime, neither did the Sahaabah (may Allaah be pleased with them all) did not do that either, as far as we know. So it is better for the believer not to do that and not to read Qur’aan for either the dead or the living, or to offer salaah or fast voluntarily on their behalf, because there is no evidence for any of these things. The basic principle regarding acts of worship is to refrain from everything except that which is proven to be enjoined by Allaah or by His Messenger (peace and blessings of Allaah be upon him).
With regard to charity, this may benefit both the living and the dead, according to the consensus of the Muslims. Similarly, du’aa’ may benefit both the living and the dead according to the consensus of the Muslims. But the hadeeth mentions that which has to do with the dead, because this is the point concerning which people are confused. Does it benefit them or not? Hence this hadeeth was narrated from the Messenger of Allaah (peace and blessings of Allaah be upon him): “When the son of Adam dies, all his deeds come to an end, except for three: ongoing charity, beneficial knowledge or a righteous son who will pray for him.” Because it is known that death puts a stop to all deeds, the Messenger (peace and blessings of Allaah be upon him) explained that these [three deeds] do not stop. With regard to the living, there is no doubt that he will benefit from charity given by himself or by others, and he will benefit from du’aa’. If a person makes du’aa’ for his parents whilst they are still alive, they will benefit from his du’aa’. They will also benefit from charity given on their behalf whilst they are still alive.
The same applies to making Hajj on their behalf if they are unable to go themselves because of old age or incurable sickness. This will also benefit them. Hence it was narrated from the Prophet (peace and blessings of Allaah be upon him) that a woman said to him, “O Messenger of Allaah, the obligation to perform Hajj has come when my father is an old man and is unable to ride. Can I perform Hajj on his behalf?” He said, “Perform Hajj on his behalf.” Another man came and said, “O Messenger of Allaah, my father is an old man and he cannot perform Hajj or travel. Can I perform Hajj or ‘Umrah on his behalf?” He said, “Perform Hajj and ‘Umrah on behalf of your father.” This indicates that it is permissible to perform Hajj on behalf of the dead or on behalf of one who is living but is unable to do it because he or she is too old. Charity, du’aa’ and Hajj or ‘Umrah on behalf of the dead or one who is incapable will all benefit the person, according to all the scholars.
Similarly, it is obligatory to fast on behalf of the deceased if he had missed any obligatory fasts, whether they were fasts in fulfillment of a vow, or as an expiation, or any missed fasts of Ramadaan, because of the general meaning of the hadeeth, “Whoever dies and was obliged to fast, let his next of kin fast on his behalf.” (Saheeh – agreed upon). And there are other similar ahaadeeth. But whoever delayed the fast of Ramadaan for a valid excuse such as sickness or traveling, then he dies before he could make up the missed fasts, it is not obligatory to make up the fasts or to feed poor people on his behalf, because he had a valid excuse.
You are doing well, in sha Allaah, by honouring your mother by giving in charity on her behalf and making du’aa’ for her. Especially if the son is righteous, this makes the du’aa’ more likely to be answered. Hence the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “… or a righteous son who will pray for him,” because the righteous son is more likely to have his du’aa’ answered than a son who is not righteous, even though everyone is required to make du’aa’ for his parents. But if the son is righteous then his du’aa’ for his parents is more likely to be answered.