This is a great song for learning the numbers 1-5 and about simple subtraction. The children will love singing the song and acting out the actions with puppets, masks or even just with hand gestures. I suggest that you modify the song on different occasions to include a daddy/grandma/grandma/aunt/uncle /sister/brother duck who is also responsible for childcare (not always Mummy Duck!).
You could also use the song to talk to the children about safety issues and why it's important to stay close when you go outside.
The Duck Song:
This song is more suitable for older children (and teachers) but is very, very funny and catchy.