Is the intention of a mother to prepare an Iftar meal as charity for her son who lives in another city sufficient for her to receive the reward of feeding a fasting person?

If you intended the food to be an act of charity on behalf of your mother, and then you gave it to yourself as charity, that counts as charity for your mother, based on the opinion that it is permissible to dedicate the reward of a good deed to both the living and the deceased. The Sunnah has indicated that a person's spending on himself is charity, and charity given to one's family is superior.