priorities

Ok Right now with the homeschooling I am struggling with the priorities. I really want learning to be fun for the kids, but I know that there are things that must be covered... How to fit it all in and not overwhelm them and me. This month we did some fun things with Presidents and trying with the Olympics, but the time is not there. With kids in 3 different grades: 6th, 3rd, and 1st it is hard to combine too much. My first grader is just learning to read and the other two are very good readers. I have a hard time finding things to challenge my 6th grader. WE have joined a COOP this semester and it has helped to take off some stress. But sometimes they do not assign homework and that frustrates me...no work for science and history for a week. I think they are missing way too much then. So that is where I added the presidents. I still have so much of the "school" mentality. Not sure if I want to let it go. What if I mess them up and ruin some good chances for them????