Since it is the last leg of your trip you will be able to do this with no problem. Don't even need to say anything to the GA. Since it is a layover and you checked in before LAX they would have no idea if you are in the bathroom or on the 405 at departure.
The only issue may be that they won't let your checked luggage to go on if you do not board, so have your family check your bag not you on the return.