Back in the late 1800s, trains ran from Sausalito out to the coast with a stop at Point Reyes Station, which remains fairly intact today and makes a good starting point for side-trip options. You could head 15-minutes north, to Marshall, for some world-famous Hog Island Oysters, or 5-minutes south to the Bear Valley Visitors Center for a park trip, or 10-minutes west to Inverness and the seashore beyond.
Biking, hiking, horseback riding, beach-bumming, shopping, or just driving along are all great here. For a picnic lunch, head to Tomales Bay Food Co., where you'll find local cheese from Cowgirl's Creamery and a loaf of Brick Maiden's rustic bread (the best on earth); if they're sold out, try Toby's Feed Barn down the street, where you should also check out the cool T-shirts in the back. You could also hit up the Food Counter for fresh sandwiches and great potato salad.
You'll get a kick out of walking around PRS. It's very cool.