Appealing to the Beatles for Help
While the Beatles didn't specifically make children's songs, many of the students in your class will be familiar with their songs. While you could translate their songs into German (as did the Beatles), you could also come up with alternative lyrics to the tunes of the song. Here are a few examples of what I'm talking about:
Das Gelb Unterseeboot
In der stadt, wo ich geboren wurde,
lebte ein Mann, auf das Meer hat gesegelt.
Und er hat über seinen Leben in
der Land der U-boot gesprochen.
Also haben wir in die Sonne gesegelt
Und haben wir einen Grunensee gefunden.
Und haben wir unter den Wellen gewohnt
In unserem Gelben Unterseeboot.
Wir leben alle in einem Gelben U-boot
I won't go further here, you get the picture. Sometimes you need to modify the lyrics a bit to fit the rhythm of the song. In the above translation, you will notice the usage of the Imperfekt in German. When you translate a song, you might want to keep in mind some of the grammar rules you are teaching your students.
If you wanted to, you can also use some of the Beatles songs that were already translated into German including "Kom gib mir deiner Hand" and "Sie liebt dich." Because the lyrics of the Beatles are often simple, they are often easy to translate for students.