If you have books covered, how about experiments? There are lots of good books of science experiments to do with everyday materials, or maybe he needs a chemistry set? DS has my old one, supplemented with various chemicals, indicator paper etc. mostly obtained from ebay(!), and loves to negotiate experiments with DH and carry them out. He does need hands-on help which is limiting in our house, but maybe a 7yo might be able to do more with supervision rather than actual help?
We also use videos a fair bit - documentaries and Great Courses courses - ALEKS, Descartes Cove, etc. Mostly he reads though!
