To emphasize the song He Sent His Son, have the children draw pictures of something really important to them. Put them in envelopes. Start with your envelope. Reinforce how hard it is for you to send this away, but you know it's important to do it, so you are going to do it. Tell the children that they are going to put their special thing into the mailbox just like you did. When they feel a tap on their shoulder they can put their envelope in the mailbox with yours. Sing the song (a few time through, if needed) until all the envelopes are in the box. Ask the children if it would be hard to send away something very special to them. Ask them how Heavenly Father felt when he sent his Son to Earth to die for men. He did this because he loves us.
*My own thoughts are that I might just do this in SR Primary. This concept might be too hard for JR to grasp. I see too many tears in little eyes when I'm trying to take away something they love... yikes. But I think it could really hit home in SR. As with any idea on this or any blog out there, use this idea at your own discretion.
*idea adapted from Sofia's Primary Ideas.