Section 88. The selectmen of any town which accepts this section or has accepted corresponding provisions of earlier laws by a two thirds vote at an annual town meeting may pay to the widow of any person aiding a police officer in the discharge of his duty by the order or request of such officer or any of the authorities of the town, or to the widow of a person doing fire duty at the request or by the order of the authorities of the town, if it has no organized fire department, or of a person performing the duties of a fireman in such town, who dies from injuries received through no fault of his own in the actual performance of his duty, a pension not exceeding three hundred dollars a year while such widow remains unmarried, or, if there is no widow, a pension not exceeding said sum for the benefit of any of the children under sixteen of such deceased person while any such child is under the age of sixteen, and the selectmen of such town may determine the amount of such pension within said limits. No payments shall be made under this section on account of any death in respect to which compensation is payable under section eighty-nine.