Bill Nye videos on YouTube are fun for that age. I'd only caution about the episode on germs. It explained how people contract HIV. Good message about it being safe to be around HIV-positive people (especially in the early 90s when it was filmed), but I don't need to answer questions from my 7 year old about needle sharing and sex.

We've watched many of his other videos though, and all of the others have been tame. It's funny listening to them turn 90s jams into science songs. LOL