This should be the only time that you actually elicit a response from your child. Once you begin the relaxation exercise, the technique is to make it sound like it's going to be "interactive." In reality, for it to work, it has to be a monologue.
"Are you seated comfortably in your spaceship? Good. Are you ready to prepare for countdown? Good. Are your seatbelts buckled? Good. Let's begin our oxygen intake. When I give the command, what I want you to do is to take a really deep breath in and hold it for as long as you can. Then I want you, as slowly as possible, to blow it out of your mouth -- as if you were blowing out a lot of candles on a cake. Ready? Begin. Breathe in, hold it, hold it, hold it, and blow out as slowly as possible. And again...." (This should be done three times.)
"Close your eyes, and with them closed, pretend to look up into your forehead, and then keeping them closed, look in front of you and down to your toes." (This "eye-roll" is a very important part of the process. It seems, when combined with the "breathing," to cause the brain to relax.)
From here on, your voice should be slow and quiet.
"Now we will prepare your body for take-off. Relax your toes please." (Wait a few seconds.) "Relax your feet. (wait) Relax your ankles. (wait) Relax your legs ... relax your knees ..." (The goal is to include as many body parts as possible, being careful not to forget the stomach, tongue or forehead.)
When this sequence is complete, and assuming both you and the child are still awake, repeat both the "breathing" and the "eye-roll."