Talk:HuPC09/@comment-26284790-20180402135329/@comment-31119526-20180402141342

The song is called ピクニック ("Picnic"). It is partly inspired by the American song "Coming 'Round The Mountain", but most of the lyrics and melody are different. You can find the lyrics and the song's history on the Japanese Wikipedia page. In case you're unable to figure out the lyrics, my poor attempt at translation would be something like

Let's go over that hill / Blowing our whistles There's a clear blue sky / Over the meadows Let's sing cheerfully / Joining hands Lanlalala Lalalala Lalalala a duck Lalalala and a goat Lala unite our voices / Match our steps What a pleasant day

The "lalala" lines match the melody of "Coming 'Round The Mountain", but the others are different, which is why I think using that song as 'translation' of what the kids sing in episode 9 isn't very accurate.