What about Cosmos by Carl Sagan? It's a bit old (different cloths, the picture is of less quality and some of the science is outdated), but still very much up to date, and I think that it was primed at all members of the households, ie. also childrens and young teenagers.
I was going to suggest that one. I have the entire serie, I will package it on torrent when i hit toronto. You might even be able to get her to watch it and pass it under the radar.
And Richard Dawkins Growning up in the universe was also intended kids, but that's not a documentary but a lecture (and also a bit old, so we have issues with cloths, picture and science).
Tough to slip this one, no?
I think the best answer to give a 10yr old, also by Sagan, is to tell the kid "I do not know". Such a simple answer but so hard for people to come up with as no one wants to appear like an idiot to a kid.
"Uncle Kafirist does not know"
