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:

1. Is there a parent who the child sees more or less often than the other? What will one do in case one parent dies, or in case the child has a language disorder, or there is otherwise some sort of unexpected problem that could impact the child's language development?
2. What are the language dynamics at play in the family and in the local area? What will the child associate with each of the two languages? Can the child have all its needs met in the non-dominant language? Does the child have access to a broader community of speakers, and in what way?

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.