Whale Rock has it all.
Amazing views of the ocean made all the more interesting by the Ten Mile River which flows into the ocean here. I would be quite happy just watching that all day, with waves sometimes going in three directions at once. You can look from the dining room, the sheltered porch or the seats at the end of the garden, depending on the weather.
Eighty five steps down to a lovely sandy beach (though there were several inconsiderate dog owners who thought they need not clean up after their animals) where the kids (8 and 12) would have played happily all day every day.
A 2 minute drive or a 20 minute walk across the Ten Mile River takes you to several miles of almost deserted beach and amazing dunes. We had fun spotting all kinds of tracks: from mice and deer to mountain lion (very big cat prints, no claws!). And finding abalone shells and whole sand dollars, and just playing on the huge expanse of sand.
The house is lovely, beds are comfortable (although a Queen for the two kids to share was not ideal, they probably won't do it in another year), hot tub lovely and kitchen well appointed. Table tennis in the garage was a fun bonus. Lots of DVDs and videos to choose from too, in case the ocean is not enough.
And proximity to all the gorgeous parks of the area: this time we spent days at the Mendocino Botanical Gardens, Jug Handle Preserve, Russian Gulch, MacKericher State Park and the Mendocino Headlands. But last time (4 years ago) I think we only went out on two days altogether, there was so much entertainment right there at Whale Rock.
We have stayed at 10 or more places in Mendocino over the last 25 years, and this is our favorite.