Speaking of the famed Koss driver, just remember that you can mod the capsule wiring with resistors to keep the volume at a safe limit.
I bought "kids' headphones" for my son because they had this feature. The headphones are not that great, and I say this outside of my expectations as a head-fier. They fall off, they're dual entry, and he probably wants a circumaural like Daddy's anyway (though his can be much smaller). I should have realized on my own that I could have thrown him one of my spares, volume-limited for pennies.