Health care rights for an unmarried couple.

I am a 45 yr old female that is living with my 39 yr old boyfriend for almost two years now. I have 2 teenage daughters and my boyfriend doesn't have any children. We have chosen not to marry at this point because of financial aid that I might lose for my college age daughters.
We live in my house and my boyfriend treats my daughters as if they were his own. (Better than their bio father) Here lies the problem...if something serious were to happen to my boyfriend and he needed someone to make health care decisions for him, would a witnessed notorized paper saying I had all legal stance be enough. He had a falling out with his family a few months ago and wants nothing to do with them but I am afraid that if something should happen to him they would not allow me to be a part of any health decisions, etc. - Is this your question? Add additional information