Each widow of a Chief State’s Attorney, deputy chief state’s attorney or state’s attorney who elected under the provisions of section 51-278 to be included within the provisions of this section, if such attorney died while holding such office or after his retirement under section 51-49 or 51-287, shall receive, monthly, an allowance equal to thirty-three and one-third per cent of the salary of the office which her husband held at the time of his death or retirement, as such salary may be changed from time to time. If such attorney leaves no widow, or if she dies before the youngest child of such attorney reaches the age of eighteen, such pension shall be payable, until such child reaches the age of eighteen, to his guardian, for the support of such child and any other children of such attorney under the age of eighteen.