If you’re looking for a beach vacation where you can actually swim in the ocean, you might want to try further south. The water in Northern California is quite cold — even in the summer — and even hardy types like surfers wear wetsuits in the summer.
If you just want a quiet spot for family fun, try the Capitola-Santa Cruz area. They’re quite close to each other. Santa Cruz offers a boardwalk, beach, a fishermans whart, and sand volleyball. Capitola is quieter with less to do but a better area for kids who want to hang out at the water’s edge.