"Hey, I've seen your kids do angel shifts at #39c3. Isn't that illegal child labour?"
Good question. Let me go full governance, risk and compliance nerd on you. Here's a legal analysis, including an initial policy and guideline proposal to formalize current compliance practice: https://github.com/andreasdotorg/engelsystem/blob/ela/doc/legal/index.md
tl;dr: smaller kids accompanying their parents at their angel shifts aren't actually working, their parents are. Older kids doing shifts on their own fall under certain exemptions that make this legal, given parental consent, time limits and suitable work.