Try this rhythm as an ostinato for the song Kalele which I posted a couple of weeks ago:
If you are using a djembe, play the low notes as bass notes and the high notes as tones. Or use whatever unturned percussion instruments you have. It might be a good idea to add words, especially if you are using different groups of percussion instruments, eg
“drum, drum, drum stick-stick drum”
Or even see if the children can come up with some good ideas for words?