Another left of field suggestion is "The Word Spy" by Ursula Dubosarsky. My daughters are reading Ursula's books at the moment. They're whimsical and lovely, looking at the development of the English language - we're up to the bit about where the alphabet came from, why it has 26 letters, etc. It's more about grammar, wordsmithing, etc. than Latin roots but it's nice to see that there are texts out there that encourage kids to fall in love with language...
jojo
http://wordsnoop.blogspot.com/http://www.penguin.com.au/products/9780670072279/word-spy
