Rent a bike and put it on the back of the van (rack holds 5 bikes). After arriving at trailhead lock up bike then hike on your own schedule for as long and as far or as little as you like. After hike, unlock bike and ride it back downtown. (1/3 of the way is downhill, 2/3 flat.) There are two reasons why people do the Combo. One, to be on your own schedule and spend more time hiking in the mountains. Two, for the thrill of riding a bike downhill.
The Combo is not for everybody. The Combo is only for confident, competent, seasoned cyclists. If you are uncertain about your ability to safely ride a bike down a steep, narrow trail or road, take the van in both directions instead. You can still go for a bike ride before or after the hike on the Coastal Trail which is the superior biking experience anyway. The "SPLIT" saves you $2 on whichever activity you do second.
If you have no doubt about your biking ability and you are 100% sure you will not be in over your head, there are four primary return routes to consider. Driver will map out your chosen return route at the trailhead. Also, if you sign up for the Combo, you must check-in at the bike rental between 11:30 and noon to be fitted with an appropriate bike.