My recommendation is to only work on four out of the eight primary songs. I found that was the perfect amount of time to work through all four songs plus four wiggle/reverent songs.
I began by telling the children how excited I was that it was fall. So many good things happen this time of year. The leaves change, the primary program is coming up, and I get to pick apples off my tree to make applesauce! I told them that sometimes I have the unpleasant experience of finding green worms in my apples. I told them I brought one of those apples today, and it just happens to have a green worm in it. Now, this isn't just some ordinary, run-of-the-mill worm...this just happens to be Winston the Worm. Now, Winston happens to love love love primary music...and when I told him that you were practicing for the up coming program...he told me he really wanted to come and hear you sing. But, Winston is a very shy worm. He usually doesn't come out of his apple unless everyone is reverent, singing their best, and smiling as big as they can so he feels welcome......(you can say whatever comes to mind for you....)
Have the children sing one of the program songs they are really good at. As you notice everyone being reverent and smiling, slowly bring Winston (your hand) out of the apple. I tended to ham this part up a bit....he came out a bit and then shyly went back in a poked his head out a bit and finally came out of the apple and waved hello. Have the children wave back to him. I asked Winston if he wanted to hear some more songs. He nodded and then waved me down to his mouth...I pretended that he was whispering something too me. I turned back to the children and said...Winston really wants to hear you sing...."fill in the blank on whatever you're working on"....and he really loves it when he can hold the Strong/Soft sign. Put the sign into Winston's mouth. Have the children follow his direction.
I could go on, but I think you get the point. Just do what comes natural to you. At one point, I had Winston smile huge (just extend your thumb and pinkie as far as they go)...the kids really loved that and felt good they were making him feel so welcome with their singing. I also had him sing along at one point, but because he's a worm you can hardly hear his little voice....
One little sunbeam jumped off her chair towards the end, came up to me and said, "Winston is just a sock!" I put my finger to my mouth and said, "Shh, he doesn't know that....let's not tell him it would hurt his feelings." She smiled and went back to her chair.
I sometimes had Winston introduce his siblings. Winston would go back into the apple and a sibling would pop out of the hole. Each Sibling had a favorite wiggle they lead the kids in.
This was such a fun 20 min. Have a great Week!