"Who climbs the Grammar tree distinctly knows
Where Noun and Verb and Participle grows." -John Dryden
I love fun grammar books. For those of you who consider "fun grammar" to be an oxymoron, you might consider A Living Grammar by Winifred Watson and Julius Nolte. Currently OOP, but a few copies still available at a reasonable price, A Living Grammar is appropriate for all ages and is a delightful introduction and review of the eight parts of speech.
Originally published in 1938, my copy is a fifth revision (1969). Way back on September 26, 1938, Time magazine wrote a complimentary review that is worth reading here. None other than Eleanor Roosevelt praised this book. She said,
"I want to tell you of a little volume which your whole family may enjoy and find useful. I was given a curious rather haphazard education. My English grammar was sadly neglected. My grandmother had a theory, I think, that you learn to talk by ear and that association with people who spoke English correctly was more important than learning out of a book. Therefore, Living Grammar by Winifred Watson and Julius M. Nolte is a find for me and you may find it a pleasant companion...Reading this book is quite the most delightful method I have found of learning grammar or of reviving the grammar we once knew and have forgotten."
The simple drawings by Shizu Matsuda are pleasant, too. What better way to begin your study of grammar this school year!