Ask HN: Teacher puts video of kids' activity online. What license is best?

Imagine a teacher/educator does a computer lab with kids and wants to film some of the activities and put them on youtube; little boys and girls would appear in the video saying they're having fun etc.

What agreement/license with kids and parents is best to have?

You can assume the video has no lucrative purpose, but the internet being what it is, things can happen like virality, links and references out of the original context and whatnot. Just asking "are you okay with this being online?" seems a little shallow, given you're dealing with minors. And besides, a proper license looks like a more sound approach. I know you're probably not a lawyer, I am just looking for a general advice.

EDIT: spelling