John Fahey (see my other thread on this forum!) though a lot of his stuff is very somber.
Bobby McFerrin has a lot of very positive and interesting music.
More positive but less interesting is an Australian dude named Mal Webb. He's very very silly, almost overbearingly so, but he has so much fun making music--you can tell that with every lyric he sings, he's got a big goofy smile on his big ugly head. He does weird things with his voice and plays a variety of instruments. His lyrics have a lot of rhyming.
http://www.myspace.com/malwebb1
"Dodgy" is probably the best song on there, hahaha.
THIS SONG is wonderful!
My kid(s) will be exposed to a variety of crazy things.