I think the effort is noble, but before you suggest to anyone else that you'll host it, I'd suggest you find a third-party cloud provider instead.

(Know that I'm the author of a commercial, self-hosted photo and video library app!)

Humans can be wonderful, but holy crap they can be quite the opposite as well. Parents are not an exception, and kids default to monsters when behind a screen.

Self-hosting this puts you in the crosshairs of moderation of both content and comments.