Gathering on the third day with the bereaved family to recite the Qur'an and granting its reward to the dead person is not permissible.
Reciting Tahlil, Tasbih (saying: "Subhan Allah [Glory be to Allah]"), Du`a' (supplication) or reciting the Qur'an over pebbles one thousand times, or more or less and putting these pebbles upon the grave is a Bid`ah. The Prophet (peace be upon him) said:
Anyone who introduces anything into this matter of ours (Islam) that is not part of it will have it rejected.
Agreed upon by Al-Bukhari and Muslim.
There is another wording of this Hadith that is:
Anyone who does an action which is not stated in this matter of ours (Islam) will have it rejected.
This narration was reported by
Muslim in his Sahih.