Everyone else has summed up the camping situation pretty well but there is another option sort of in the area. All the way at the mouth of Tomales Bay is the strange little town of Dillon Beach. Lawson's Landing is a private RV park there with boat launch and pier fishing facilities. I have never stayed there as in the old days it had a pretty rough and tumble reputation, but I know people that camp there regularly these days and it seems to have calmed down. There is decent clamming there if you are able to get out on the tidal bars at low tide. I think this is the only option in the area for camper camping right on the beach.
Some things to do while in the Pt Reyes area:
The Station House Cafe in Point Reyes Station used to have house made butterscotch pudding on the menu, and it was amazing. I don't see it on their menu now unfortunately, but their food is good if you like coastal fare. If you like oysters, drive north along the east side of Tomales Bay. There are several oyster farms in the area, but the northernmost one, Hog Island, is worth the extra drive. We bring a cooler with ice, our oyster knife, a lemon, and some beer, then stop in and buy a few different crustaceans. I like getting a dozen Kumimoto oysters and a dozen manila clams. We go eat somewhere scenic, but a lot of people eat right there at Hog Island. They sell everything you need, from styro coolers and ice to oyster knives.
If you have kayaks, you can launch from Nick's Cove near the north end of the bay. This year has been a good season for halibut in the bay, and even on windy days, Pt Reyes protects the bay pretty good. We fished the bay last year for halibut, but in typical fashion failed miserably. I managed to foul hook a decent Silver salmon when I was trolling, the only one I've ever caught. Kind of sad to release it knowing it was probably leopard shark food. And if you don't have boats, you can fish for Leopards from shore with decent success. If you really want to catch a Leopard, you would want to head south to Bolinas lagoon.
As mentioned elsewhere there are several boat-in campsites along the Tomales Bay side of Point Reyes, but some of them have no facilities and you are required to pack EVERYTHING back out with you. EVERYTHING. Meaning an embarrassing bucket of shame has to come back with you.
In the actual National Seashore, there are several fun things to do. You can go check out the lighthouse at the southern point which involves minimal walking, or you can take a long stroll on North Beach (working on a salmon boat you probably have heard it called 10-mile) and check out the driftwood there. At the north end of the park, there is a decent day hike from a historic farmstead down to the coast. The somewhat legendary and out of place Tule Elk tend to be around that northern part of the park and you are likely to spot some on that hike.
