I did a fun one today that had the kids total attention.  First we sand When we are helping ...then we talked about Nephi and his bow...and how even though his family were complaining against him he still went back and served them by making a new  bow.... then we discussed a few other scripture stories of service within our families... For ex Mormon and Moroni writing  letter to each other,  Alma praying for his son, etc.  Then we sang Give said the Little Stream.  While they were singing I slipped out of the room and put on my trench coat, a hat, and sunglasses.  I came in real sneaky.... Then proceeded to tell the kids my name was Priscilla Primary and I was a secret agent on a TOP SECRET mission.  I then proceeded to tell them that I was to assign them a top secret mission.  I gave them all a cut out of a snake (a friendly looking one that I got off the internet ) with a poem.  The snake was called "Sally the secret service snake."  The poem went like this:
 

 

Then I explained to them that their secret mission was to go find someone in need at home.  When they had done a secret act of service then they left "Sally" there.  Then when that person found Sally it was their turn to do a secret act of service.  So soon everyone is doing secret acts of service for each other.  Then I bore my testimony of how when we serve each other a wonderful feeling comes over us and in our home.  Everyone will be happy and want in turn to make others happy.  It really went over soooo good.  The "secret agent"  really got the kids attention Junior and Senior Primary.  We have like 105 kids in primary so sometimes getting all their attention is hard...but this worked wonders!