I trust the process. For me, that means pointing out the parts of speech and punctuation through daily copywork and narrations. If you have the components you need (rich literature, copywork, narrations), you won’t need to supplement, especially for a 3rd grade student.
With that said, if you want to add in some light grammar, feel free. I have used English For the Thoughtful Child, both volumes, Emma Serls Primary Language Lessons, MadLibs, Word Roots and the Pathway Readers Language Arts workbooks (we won’t finish the one we have).
I’ve used these products just because we can, and they’re quite sweet. But we have not used them consistently. Most of the time it’s been to give my dc something independent to use or when I’m having a bad day with my health issues. I may pick up something for my 12yo to give him something because of my health but I’m not quite sure.