Legal Question in Wills and Trusts in California

No. You will either need a codicil drafted to your will or have an entirely new will drafted. I would recommend the latter.

Sounds like you need a new will drafted. I personally don't like codicil's

also, neither wills nor codicils need to be notarized. They must be signed by two witnesses.

If you try to do it yourself, there's a substantial chance you'll make a mistake as you've already been informed above. Incidentally, if you make your own will and it's witnessed by two persons, both witnesses have to be adults and neither can inherit anything from you.

If you have a lawyer prepare your estate plan, then he or she will be a neutral disinterested witness as to your mental capacity and your intention to disinherit your son. The lawyer can also keep your original will in his or her safe, so that your son can't make it disappear if he shows up at your home first after your deaths.

While it does cost money to have a will or trust prepared by an attorney, consider how much your chosen beneficiaries would have to pay in legal fees and a loss of all or a portion of their inheritance if you don't do it right.