Songs are the greatest! Pardon my not so great voice, but preschoolers don't care, so don't be afraid to sing yourself. This is a student that I do private lessons with and one of his favorite gym songs! Songs grab preschooler's attention. They also give you a leadership role in the class if you need to grab the focus back to you, especially if you are the one singing and it is not just a cd.
Now, not ideal for stretching, so please don't use this to teach preschoolers to stretch pikes. But I have found this is perfect for teaching the pike position! Before we sing the song, we go over what that position is called and what it should look like.
Notice that his pike is not perfect when we sing. That is OKAY. He will learn. It will take a couple times practicing it.
As a bonus, I throw in a rough teach of the tuck and roll position at the end of the song.