Does this sound like a reasonable plan. Midweek in August pick up hire car in downtown SF around 9.30am and drive via Hwy 1 to half moon bay for a short refreshment stop. Continue down Hwy 1 to Santa Cruz for lunch - stop for around 2 hours. Take Hwy 9 to Henry Cowell Redwood park and do the short loop trail - stop for an hour or so. Head back to SF via Mt Herman Road, Hwy 17, Hwy 85 and Hwy 280. Drop the hire car off in SF around 4pm. According to Google maps the drive is around 160 miles/3hrs and 9 mins so it would seem that the plan is realistic subject to traffic and driving conditions.