Talk about each experience your child will face and how to handle it. Let them know you will be there with them. When your child is connected to a respirator they can't talk. This is scary. Make some simple signs for pain so you can communicate.
Some children ask about dying, even with non-serious surgeries.
It is serious to them. Prepare ahead of time how you will answer them, should the need arise. Remember be positive. Making preparations ahead of time, for after surgery, reinforces to the child he will live. Practice signs if your child will be on a respirator or have throat surgery.