When composing a song for young children, I try to think about it in terms of choral-ography. In other words, I always try to imagine how the children would interpret the song on stage. The words come across best when simple gestures can be used to emphasize the meaning. Words suggesting a direction such as "up" or "down" I make sure have a gesture or body movement to emphasize that. Lyrics about joy or love or happiness might have a gesture of clasping hands at the heart. Lyrics about sadness might used slumped shoulders and frowning faces. Words with abstract meanings are the most difficult to interpret. I usually save the simple generic hand and arm motions for those lyrics --- arm out left, arm out right, both arms up, one arm up in back and one down front with "jazz" hands (fingers wiggling), etc.
First-time actors are generally not trained dancers. So only very simple foot movements can be used. Variations of walking, sliding, or spinning are about the extent of full body motion that can be safely used. Kids usually have trouble with Right and Left and other stage directions, so I try to remember to keep it consistent by always starting on the same foot or turning in the same direction with succeeding passages. It is crucial that when you begin teaching choreography of any kind, you continue practicing what you started. Making a lot of changes just confuses them and they don't know what to remember. Most kids tend to remember the movements you taught them first. So figure it all out before you get started. With enough practice time, it is surprising how proficient kids can get at their movements.
And remember that if you work in front of the group facing them, you must "mirror" their motions. If you use your right hand, expect them to use their left hand. Be prepared to reverse that if you turn around to face the same direction as the group. Using "Choral"-ography is a great way to have your group interpret the songs and give a polished performance!