Generally a trust amendment in California is not required to be notarized unless the trust requires it. BUT -- it should be anyway because it will need to be if it is recorded. Also, it's good to have it notarized to prove the date it was amended and not forged.
However, based on your question, it seems you are probably considering amending the trust without an attorney. That I don't advise. Amending a trust is tricky and easy to mess up. That could just result in further litigation down the road. So, my advice is -- go see a lawyer.
