If you want to teach your older child physics, you can hardly find a more thorough and inspiring introduction than the Feynman lectures. The hardcover version costs over $150, but all the lectures are now available online in edited by Caltech written form for free. There are links to video lectures as well. I started reading his introduction to science and physics and they really are brilliant. I’d love to know how early an EL kid could get started with these in a homeschool setting, I would think around 10 or 11 years old? What do you think?
News article with link to videos:
http://io9.com/you-can-now-access-all-of-richard-feynmans-physics-lect-1627809095
Openculture link to the text books:
http://www.feynmanlectures.caltech.edu