<span>You need Mi mamá y yo preparamos la cena in future tense. To make this sentence future tense, the conjugation of preparamos must change. There are two people who are going to prepare dinner some time in the future (you and your mother). That means preparamos must be conjugated for the plural pronoun nosotros ("us/we"). The future tense conjugation of preparamos for the pronoun nosotros is </span>prepararemos. Replace this with preparamos in the original sentence and it becomes future tense.
Mi mamá y yo prepararemos la cena.
