We have this book and love it, but I wouldn’t go very far into it with an 8 yr old. You don’t need any grammar book at 8. Does your state require you to use a book to teach grammar, or do they just require you to teach it? I only taught my 8 yr old nouns, verbs and adjectives.
After I read some of a book to the kids, I read them a sentence from the chapter and ask them to tell me all the nouns, or the verb or adjectives. They love to pick them out and are very satisfied–and so am I. My 7 yr old is especially good at adjectives. His dad couldn’t even do it!
It seems like that’s as far as actual grammar needs to go for now. When my oldest was young, we spent 3 years on adjectives in workbooks. What a waste, this way seems to be so much more practical.
Good luck!