Good luck mickie, I really do hope this fast helps you achieve true clarity and the change you need in your life! Why does your 8 year old think you are going to die? Because you are depressed from all your hard times or because you aren't eating? If it's because you aren't eating it's an opportunity to educate him about the realities of fasting. Let him know the benefits of fasting and how safe it is, be totally up front with him. If he is worried about you he deserves to know anyway and it will be fantastic for him to learn at his age.
As long as you listen to your body your fast will be safe and that is the message you need to get across to your son. Your main goal with this fast may not be physical health but for your own sake and for the sake of your family you need to monitor your physical state also. Your son may just need some reassurance that you will be doing this also during your fast.