well, children's music is a big business here and there are actually many rock/metal projects for kids in Finland which all are pretty much based on cover songs with childrens lyrics (for example the "jee hevisaurus" song is based on kiss' "heaven's on fire") and most of the times the guys making are like professional musicians from top of the line bands.
Moottorin Jyrinä
Ratz
Pikku Orava
Hevisaurus
Fröbelin Palikat (this is actually one of the best selling bands in Finland of all time, for real)
Smurffit (the fuckers that started this thing back in 1996 or something, the first album in the series is one of the best selling albums of all time in Finland, selling 5 times platinum and the 17 albums on the series has sold over 750 000 albums, and considering that there is only 5 million people living in Finland, thats a helluva lot)