I am sorry for the pain you are in. As this family situation plays out, you'll know how to respond. There's no "right" or "wrong" way. As for "staying positive," you needn't pretend anything. You are entitled to your feelings as you learn more about the "reality" of the situation.
Self-compassion, along with compassion for others may ensure the best outcome.
Please take good care of yourself as you and your family negotiate these bumpy roads.

WC