Fill the gas tank, add some Sta-bil Gas Treatment, change the oil & filter if you haven't in the last 2000-3500 miles or so. Clutch and brake hydraulics ought to be fine in the temperate San Diego climate.

If you want to be fussy, get the car up on jack stands to keep the tires from taking a "set". If your parents are going to drive the car once a week, you can skip that step.

Will the car be parked in a garage?