There are many apps that he might really like- from Stack the States and Presidents vs. Aliens to Oregon Trail and versions of all the main documents.
We are also very partial to icivics.org!
If you're looking for books, check out Horrible Histories, and the "You Wouldn't Want to Be ___" series as well.
Keep an eye on
http://homeschoolbuyersco-op.org/ where they often have Discovery Education specials for homeschoolers. I haven't seen that ebook version, but they may have it in the summer for next year.
