Reference: Fataawa Noor ‘alad-Darb – Question No.6448, Pages 276-277, Volume 12
Question: What is the best thing a child can do for his deceased parents? [Bearing in mind] I fell very short [in my care] towards them, since I was overseas when they both died. I need a response [to my question] so my heart can be at ease. I have now returned back to my country [and have become religious]; I am of sound ‘aqeedah, and I maintain my [obligatory] prayers, and regularly frequent the masjid, so is it sufficient for me just to supplicate [for them]?
Response: Concerning your parents, so long as you did what you were able to do in terms of honouring them during their lifetime, you are not required to do anything more. [Now] that they have passed away, [from that which] you should [do to] honour them is to supplicate for them, seek forgiveness for them, give charity on their behalf, honour their friends and maintain those ties of kinship which exist because of them.
So, all Praise is due to Allaah [alone], based upon what I have understood from your question, you are upright, and keen on honouring your parents, so increase in supplicating for them; and with that you will accomplish complete honour towards your parents in their lifetime, and after their death.