Is it permissible to slaughter a calf instead of a cow for a vow, and is it permissible to give the mother and sisters some of the meat from the vow, and is it permissible for the husband and children to eat from the meat given to the wife's family?

The one who makes a vow is obligated to fulfill what he vowed if it is an act of obedience to Allah, and it is not permissible to change it as long as fulfillment is possible, based on the Prophet's (peace be upon him) saying: "Whoever vows to obey Allah, let him obey Him; and whoever vows to disobey Allah, let him not disobey Him." Therefore, slaughtering the vowed cow is obligatory. It is permissible to give some of its meat as a gift to relatives and the spouse, unless a specific recipient was designated for its distribution.