Do you have to report to K12?
If not, I can tell you that we had great luck with just checking books out of the library that interested DS back when he was 6/7. Especially in science, this worked really well for him. To make sure we weren't missing anything important, I just used guides like "What your 1st Grader needs to Know" by E.D Hirsch
http://www.amazon.com/What-Your-First-Grader-Needs/dp/0385319878 and websites like this one:
http://www.worldbook.com/typical_course_of_study.html. But especially in science, there's a lot of variety about what kids learn. There isn't one "right" course of study. As long as the kid is learning something every day and you move between all the sciences (earth science, biology, astronomy, etc.), you'll cover the bases.
Every kid is different, so do with all this what you will. But for us it was great to be able to study things that interested him at a pace and level of complexity that suited him, and the library books are free. FWIW, three years later, at age 9, DS is a science whiz, way ahead of his age-peers in terms of what he has been exposed to in science, so it definitely didn't hurt him to go off-road.
The first year for every homeschooler is a learning year. You're figuring out what works and what doesn't. That's normal and healthy. Really, it sounds like things are going well for you. (Even if it doesn't feel completely like it is...)
