Praise be to Allah.
It is not sufficient to give money instead of what is required because of a vow, unless what was vowed was to give money as an act of worship to Allaah, in which case it is permissible to give the money as one vowed to do. But if a person vows to give all his wealth, he is only obliged to give one-third of it. Similarly it is not sufficient to give money for an ‘aqeeqah or waleemah (wedding feast) because the Sunnah regarding ‘aqeeqah is to slaughter two sheep for a boy and one for a girl. And the Sunnah regarding the wedding feast is for a man to give a feast after he gets married, even if it is with only one sheep, because of the saheeh report from the Prophet (peace and blessings of Allaah be upon him), according to which he said to ‘Abd al-Rahmaan ibn ‘Awf, after he got married: “Give a wedding feast, even if it is with only one sheep.” This is the Sunnah in these cases. Spending money instead goes against the Sunnah and there is no basis for doing that; the Prophet (peace and blessings of Allaah be upon him) did not do that and neither did his companions (may Allaah be pleased with them) after him. So we should adhere to that which is narrated in the Book of Allaah and the saheeh Sunnah of His Prophet (peace and blessings of Allaah be upon him), and not do anything else.
And Allaah is the Source of strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions.