I love Beautiful Feet. I know they have both a middle school and high school guide that you could use with your 7th and 10th graders. It's a literature approach to history so they get to read great fiction and non-fiction books, plus do things like maps, etc. that you could play up for your military interested student). It's minimal on your time in preparing and teaching (though its always good to review material with your student. Not expensive and most books can be found at library. Your 7th grader may focus more on certain biographies while your 10th grader wants to dwelve more in the battle plans. So they both cover American History but focus on certain aspects of it. I love Beyond Five in a Row for 3rd grade and up, as it is also a literature based unit study. It covers language arts, history, geography, science, and the arts. Again most books can be found at library, and minimal lesson prep time. Hope that helps.