Keep the kids out of school tomorrow. Go get family photos done before chemo dramatically alters your appearance. Then go out to lunch and go do something you all enjoy. Spend an hour with each kid one on one and tell them that you are so sorry that you are sick, but that you love them and you will do everything you can to get better. Tell them that they might feel scared, sad, angry, whatever and that those are all allowed. Give them each a big hug.
In the next few days, notify teachers, activity leaders, school counselors, religious leaders, etc. who might be abme to help smooth things for your kids during a rocky time. You should also look for a family therapist. Wishing you and your family lots of peace!