Praise be to Allah.
Among the fatwas issued by the Standing Committee for Issuing Fatwas is the following:
We do not know of any evidence (daleel) from either the Qur’aan or Sunnah to indicate that it is prescribed to recite any soorah of the Qur’aan in any place, or in the house of the deceased. We do not know of anyone among the Sahaabah or Taabi’een or Taabi’ee al-Taabi’een [i.e., the first three generations of Islam] from whom it is reported that he did that. The basic principle is that this is not allowed, because the Prophet (peace and blessings of Allaah be upon him) said: “Whoever does any action that is not in accordance with this matter of ours [i.e., Islam], will have it rejected.” (Narrated by Muslim, al-Aqdiyah, 3243). With regard to gathering and making du’aa’ for him, du’aa’ is an act of worship, and acts of worship are based on the principle of tawqeef [i.e., to be based solely on the saheeh texts, with no room for adding or taking away anything]. It is not reported that the Prophet (peace and blessings of Allaah be upon him) made du’aa’ with his companions for any deceased person after he had completed the (funeral) prayer. It was reported that he used to stand by the grave after the ground had been levelled over its occupant and say, “Pray for forgiveness for your brother, for he is being questioned now.” From the above we know that the correct thing is not to offer a collective du’aa’ after offering the funeral prayer, and that this is bid’ah.
Fataawa al-Lajnah al-Daa’imah, 9/16
So pray for your deceased each one of you individually. It is OK to make du’aa’ for him during salaah and at other times, at the times when du’aa’s are answered, such as the last third of the night, the last hour of ‘Asr, Fridays, between the adhaan and ‘iqaamah, etc. You should be sincere in your du’aa’. When the du’aa’ is only between you and Allaah, you will feel more khushoo’ and will feel more sincere than when you make du’aa’ simply to please others, as when people recite du’aa’ collectively to please the family of the deceased. May Allaah help us and you to do all that is good.