I had a couple new-ish choristers ask for details on the hot/cold game so here you go!
Pick an object to hide, we've used a pass-a-long card, a toy car from my diaper bag, a little laminated CTR shield...really anything will work.
You have one child leave the room (have a teacher accompany if needed)and give a 30 second time limit for a second child to hide the object. I must pass along my knowledge by saying that it's important you make rules for the hiding such as; no hiding object on another person, and at least part of the object must be in view.
Bring the child back in and begin singing getting louder when they are "hot" (near the object) and quiet when they are "cold." it's a perfect review game and fun plus it introduces the concept of dynamics perfectly! Have fun with it and coax the singing by being overly dramatic in your own louds and soft!