Kids are famous for rising the audio to 11 just for fun.
I am not writing about youngsters and rock but toddlers and kids listening to walkman/mp3-player/whatnot that for a shorter or longer time raises the audio volume to hearing damaging levels.
Why not create headphones that are limited in themselves. Electronics it them limit the amount of energy allowed to push through. Since the mechanics of the ear phones are known it shouldn’t be too difficult.
Babysitting your own children and out of ideas of what to do that is both educational, fun and social?
Why not have a site that is geo sensitive and keeps discussions about local happenings. Think opening hours of museums, position of play grounds, public transportations maps, happenings, eating possibilities. It should be crowd sourced so the parents themselves use and update it. Then big enough so the local businesses (museums, stores, kiosks) updates it to draw more customers.
This idea can be made universal to handle almost anything “what should I do today” but limiting it to parents and their children could be a good idea to make the subject narrow enough to be usable.
If you local surroundings aren’t interesting enough for such a site, think visitors and yourself travelling with children.