If you were cited for VC 14604(a), the DA must prove that you "knowingly allow[ed] [your son] to drive the vehicle upon a highway [without] determin[ing] that [your son] possesse[d] a valid driver’s license." I assume you were aware that your son did not have a valid license, but your statement that you were "unaware of anything up until[] [the] moment" that your daughter called you suggests that you did not "knowingly allow" him to drive. Whether you call that your son stealing your car or taking it without permission is of no real relevance, but you will have to affirmatively testify that you did not give your son permission to drive by himself, and that may result in additional consequences for your son.
I suggest you confer with a local attorney.