Okay, Craig and Julie from Seattle: the answer is Anini Beach on the north shore of Kauai.
The question? This couple with two kids e-mailed us, seeking a good place in a quiet beach front setting where their sibs and kids could gather with their parents for a family reunion. They stressed the need for a peaceful surround, and didn't care about the proximity of restaurants or shopping, etc.
Anini has no resorts or commerce, just a two mile run of reef-protected sand that offers safe swimming and snorkeling (when the usual precautions are heeded). Vacation rentals here tend to be large single family dwellings on large lots. Princeville Resort is a couple miles away, and a dinner outing to Hanalei is only 6 or 7 miles.
BTW: For a complete list of beach-cottage-type locales (along with all the other possibilities, such as mid-level family resort beach towns, country cabins, swank resorts, etc.) take a look at No Worries Hawaii, which is a vacation planning guide for all the islands.