grandpaof5,
Your son will have to do some local homework to help this out. He will need to find an FFL here that really understands the state laws of CA this may take some time. here is a like to a
form that should help him talk to the local FFL's. the phrase your looking for is Intra-Familial. This is easy if within the state, a little harder from out of state. If the long gun is listed on the banned list then it can't enter the state. Any mags over 10 rounds are out of luck. Handguns that are no on the approved CA list are exempt for Intra-Familial transfers. Good Luck!
PS make sure every gun that is sent has paperwork stating that this is a gift to you son.