Learn Spanish (Latin America): Nosotros mismos ventilamos el armario y sacudimos la ropa. - We ourselves air out the closet and shake out the clothes.

Adding mismos after a subject pronoun provides emphasis, translating to "ourselves." While nosotros just means "we," nosotros mismos stresses that we are doing the chores personally, without anyone else's help.

Would the word mismos change if a group of women were speaking?

Yes. Because it acts as an adjective emphasizing the pronoun, it must agree in gender and number. A group of women would say nosotras mismas.

Could ventilamos and sacudimos be in the past tense here?

Exactly! For both -ar verbs (like ventilar) and -ir verbs (like sacudir), the nosotros form is identical in the present tense and the preterite (completed past) tense. Without more context, this sentence could equally mean "We ourselves aired out the closet and shook out the clothes."

I know ropa means clothes, but why is it singular here?

In Spanish, la ropa is a collective noun that is always singular, much like the English word "clothing." If you want to talk about multiple individual items, you would say las prendas (the garments).