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?
Former child in a bilingual household. The time that your child spends outside of your home has by far the biggest influence on language fluency. You can have your child speak a language at home, and they would be able to understand it and speak it, but it would be limited - likely conversationally fluent, but not natively fluent.
If you can find a community for that language and culture that you visit every once a week, it will help reinforce that language. There might be language schools run by people from that culture - it’ll be an easy way to get in touch with other people from that same culture