Although I mention parents specifically in the title, this isn’t just for parents to respond.
My wife and I are trying to raise our child to be bilingual (English and Portuguese). Currently we’re both speaking a bit of both to our child and when they eventually go to school we’ll speak more Portuguese as they’ll be exposed to English everywhere else.
Is this a good approach or is there something we can do better?
I was raised bilingual, and speaking from my own experiences I'd say that it's a good idea to consider the following questions if you want to maximize the child's ability in either language:
I'm not sure if it's a good idea to share my own story because it gets pretty melodramatic at points, but yeah, language skills need to be built and maintained over the course of one's entire life, so you need to be able to adapt to changing circumstances. But as a whole I think that what you're planning for your own kid sounds like it will work well, or at least decently well — the only way to know for sure is to get a time machine and go forwards 20 years, and until then I think it's best to have faith in your competence as a parent. There's no-one who knows a family better than itself.
And beyond that, one should also ask oneself... Well, what types of language skills does one want to see in one's child, and what happens if the child ultimately does not reach the goals one has set? I'd say that I have sort of a nuanced or over-complicated relationship to so-called "bad grammar" because of my position.