More to explore:
Kidz Gear Expands Headphone Lineup for Kids with New Volume Limit Headphones - http://www.ipadsadvisor.com/kidz-gear-expands-headphone-lineup-for-kids-with-new-volume-limit-headphones
road trip and flights!
Kidz Gear Headphones for Kids
Kidz Gear Wired Headphones For Kids - Gray:Amazon:Electronics $20 has volume limiter
I Travel for the Kids: 2012 Holiday Gift Guide: Kidz Gear Headphones