Here is a web-site dedicated to heart health: Cardiac Resynchronization Therapy: which turns out to have some really great educational videos of the heart. My older children were captivated by the video available on the home page at http://www.heartlibrary.com/. In addition to the cool videos, this web-site also has a glossary of terms, a section of Frequently Asked Questions, and stories of patients.
The bottom line is; We try not to insist on parent-led learning or gravitate toward child-led learning. We try instead to focus on God-led learning and ask for His input and perspective on every aspect of our home school. That way, when others fuss about what Dan and I are doing and make me second guess our decisions -- I can go back to our decision process and find God's fingerprints, reminding me that this is His way.