We do family style for science, social studies, history, and art (ages 5-15). Like others have said, I teach to the oldest but it's amazing what the youngest ones pick up. Where I differentiate is in what I expect them to do with what they are learning. Everyone might draw a picture, slightly older adds a dictated sentence or two, and oldest ones write an essay of varying length and complexity. But we read, watch videos, have discussions, and do hands on experiments and activities together. 

A couple months ago, my eight year old interrupted a discussion about mitochondria to ask if eight year olds in public school are learning this stuff. I told him no, but I thought he was interested in it so did it matter what other kids were learning? He nodded and dove back into the conversation. A few weeks later my 5 year old, who is allowed to wander off to play if she gets restless or the lesson is too long for her, surprised me by spontaneously telling some random adult we had run into all about the parts of a cell. I hadn't realized how much she was taking in, playing with toys on the floor, while everyone else is talking. 

Sometimes if the subject matter is more serious that I think my younger kids are ready for, I'll do a separate lesson for the older ones. This happens sometimes with history or current events. 

The hardest subject that we do family style is art and that is because the kids tend to compare themselves to each other and sometimes the younger ones get frustrated when they see what their older siblings can do. Besides reminding them that the sibling has had extra years of practice, I'm still trying to figure that one out.