A. On and after September 12, 1980, if a member of the police departments of the cities of Opelousas and Ruston dies while in police service, while on or off official duty, or while receiving a pension, and leaves a child or children under eighteen years of age, or a child or children who are under twenty-two years of age and who are full-time students at an accredited institution of higher learning or at an accredited trade or vocational school, or a widow, or a dependent mother, these survivors shall be paid as follows:
(1) Each child who is under eighteen years of age or who is under twenty-two years of age and enrolled as a full-time student at an accredited institution of higher learning or trade or vocational school: one hundred fifty dollars per month.
(2) A widow: four hundred dollars per month for as long as she remains unmarried.
(3) A dependent mother: one hundred dollars per month.
B. The benefits provided for in this Section shall be paid to all beneficiaries, including those whose rights to receive these benefits accrued prior to September 12, 1980, but otherwise without any retroactive effect.