Hi Bartlett,
You can get some good ideas from the curriculum guide on this site. Some also use Truthquest to get multi-level ideas for history. You can select a couple of history and literature books to read together as a family. Then the children will each have an age appropriate assignment to do plus you may choose to read a little extra aloud with the youngest ones. Bible, music appreciation, composer/artist studies, poetry, logic (with Fallacy Detective, for instance), map drills, geography, art, and hymn studies are all subjects to easily teach in a cohesive manner unless there is a need to individualize through necessity or the appeal of a child. Again, it is the follow-up assignment that often differentiates the grades, not necessarily the material covered.
Science can also be taught as a group (I forgot to mention Nature Study above, by the way). One way would be to get a text and read it with the children, adding in explanations as necessary. If you are quite industrious, Lifetime Books and Gifts has, on their website, a list of resources by creation day. Also, I do believe that Tapestry of Grace had, at one time on their website, a way to make Apologia’s Physical Science multi-level. I for one, teach science separately 🙂 because I am not that industrious. However, you could read aloud some to them all; perhaps a biography or one of the Masters Books.
I do hope this was helpful versus burdensome!
Blessings,
Cindy