I really think the activity guide is a good investment, Genevieve. Initially, I thought it was just going to be hands-on projects and additional suggested reading (which in and of itself would have been great), but it is SO much more. It includes review questions, narration exercises, additonal history reading, corresponding literature suggestions, and map work, to name a few. Personally, I don't think you need to purchase extra sheets. There are 'Student Pages' at the end of the activity guide, mostly coloring pages and map work, and this section takes up more than half of the book. Also, I could be wrong, but I think I read somewhere that the extra sheets are just duplicates of what is already in the guide as the 'Student Pages'. I wouldn't want you to waste your money, so I'd just check on that to be sure. I think if you have the book and the activity guide, you'll be all set.
HTH,
Michelle