Legal Question in Family Law in California

You should speak to a competent attorney with experience in family law and estate planning issues and see if you can do a "post-nuptial" agreement.

You can always do a post-nuptual agreement. The only question is what can go in it and how to make sure it is both fair and "sticks." You will need a local attorney to work with in person on that. You can also expect to need to pay an independent attorney to at least review and advise your wife on signing it. It will be cheap insurance against her later claiming she was railroaded into signing it, and it may be mandatory depending on the provisions you include.