I have a little bit of experience in this. Brazilian living in Quebec. So, my friends almost always spoke in Portuguese with their children, school and TV were in French. After some time, school starts also to teach English and they chose the language of the TV. Now the kids are almost always speaking in English, although the are fluent in Portuguese and, of course, French.

Now, my wife and I hated the TV in French, so we kept it in English. So, my kids had to deal with three languages from the start. They mixed everything up and we screwed up by saying words in all three languages. We speak mainly Portuguese but we would use words that they learned in other languages in those languages instead of in Portuguese. In the end, my kids mix all three languages in a single sentence, which is weird as hell. They’re slowly separating the languages and we too. Now, every sentence we speak is in a single language. Their friends help in a way, because they also speak French in class but English outside (and Quebec’s government hates that).

So, if both of you are Portuguese speakers, I’d only speak Portuguese with them and let the TV and school teach English. They’ll know how to keep things separated.