Great questions. (And thanks for the encouragement! 🙂 )
When it says “books listed in grades 4-6 plus…” does that mean that the 7th & 9th graders should read all of those plus those in 7-9th?
That directive basically means that it works well to read the books for younger children aloud to the whole family. Thus the older children would also be hearing the younger children’s books. Since you don’t have a 4-6 grader, don’t worry about it.
How do I know which to do as a read aloud and which to do independently? Do you usually use the “spine” as the read aloud?
Yes, I usually do the spine as the read aloud and the younger children’s books. In your situation you could either read aloud the Famous Men books as your spine for the whole family, or skip the spine for your 1st grader and assign the “Story of the . . . ” spines to your older children as part of their independent reading (or read it aloud to just the both of them, if you want to).
The 7th & 9th graders could technically read the same books so do you let them read the books in a different order so they don’t need the same book at the same time?
That’s always a challenge. If you have them read the spine book independently, one could read the spine while the other read the additional book; then they could switch. Or feel free to read the books out of order if you want to. I think that if the children are entering dates and events and people into their Books of Centuries, they shouldn’t get confused.
Oh, another possibility might be to get one or two of those books on audio so they can listen to them together. Just some ideas. 🙂