Is the children's song familiar to anyone? I've never heard it before; perhaps it is a part of German culture. In America, we have a similar song, which begins, "Eeny Meeny Miny Moe, catch a tiger by the toe." While the song is certainly indicative of the movie's content, it also symbolizes the innocence of the children. They are merely playing, not really understanding the meaning of the song's lyrics (I hope!).
I enjoyed the mother's expression when the clock chimes. She knows her daughter is on her way home for lunch, and that makes her happy.