Nothing needs to be translated from Portuguese to English, only if you have docuements in a 3rd language you'll need to translate.
I do advise to translate the Birth Certificate 'cus it will be needed for AOS, later down the road.

Then you'll need a copy of the original and the translation (it can be a copy of the official translation, since they must be an official one and tend to cost quite a bit of money). Doing it in Brazil will be cheaper and easier than in US.