There are two possible scenarios:
(1) If the deceased left a will, what happens to the guns will be determined by the terms of the will. Unless California law differs from Federal law, inherited firearms are not required to be transferred through an FFL. However, whoever will receive any full-auto firearms will have to obtain the required tax stamps. Any firearms that are not legal to possess in California should be removed from California.
(2) If there was no will, the firearms are part of an "intestate" estate and what happens to them (and everything) is handled as California law provides for intestate succession. Federal law provides that firearms inherited through intestate succession do not have to be transferred through an FFL. If the inheritor(s) is/are from another state, then California law cannot override this.
First step is to be clear whether or not there is a will and, if there is a will, if the firearms are specifically mentioned, or just lumped together with "all my other stuff goes to ..."
The question is, what is the best way to disposition these weapons and pass them on to friends and family members.
You have to be VERY careful here. Whether there is a will or the person died intestate, one way or another someone (maybe more than one) is the legal heir to each and every one of those firearms.
THAT person or persons will be obtaining the firearms through inheritance. If he/she/they is/are from another state, only Federal law applies and there is no need for an FFL to make any transfers. Once a probate judge certifies the will (or the terms of intestate inheritance), the heir(s) can just pack up the guns and drive away.
However -- if the family decides to distribute the guns to members of the family who are NOT heirs, either because of terms in the will or because of the legal pecking order established by intestate succession, then those people will NOT be "inheriting" firearms (no matter how much it may feel like they are to them) ... they will be receiving firearms as transfers from living owners (the heirs who DID inherit the guns). THOSE transfers will require the intervention of an FFL.
The advice to consult an attorney is well-taken. This is not a question that can be answered with any authority by a bunch of people on an Internet forum who do not have complete access to ALL pertinent information.