DS (3 and a half) is engrossed with his newest playthingmy personal stereo which, until I get him his own that he can put on by himself, has ordinary adult headphones which fit into the ear. I've made sure the volume isn't up too loud, but, being an ever-paranoid parent, I'm just a bit worried that I may be damaging his ears. What do other people thinkwhich sort of headphones would be best to buy?