My wife, 10 year old son, and I had a wonderful week-long stay at the Guest House. The stream it sits on is great and we enjoyed paddle boarding down the stream to Wainiha beach.
One thing I very much appreciated is that unlike many rentals, the house includes some basic food items, such as salt and pepper, coffee, rice, condiments in the fridge, etc. We made several meals, including grilling, and had all the utensils or appliances we needed. There were also several beach chairs, umbrella, cooler, and a couple boogie boards.
We enjoyed sitting on the deck and reading. We tried to unplug as much as we could, and there was no cell service (a lot of hand made signs in the area in opposition to putting in a cell tower), but solid wifi that was easily good enough to stream movies at night.
It isn't really within walking distance of any swimmable beaches, but is a short drive (less than 10-5 minutes) to several swimmable beaches and Hanalei.
If you have a small group and want somewhere that isn't a resort and is fairly quiet, I highly recommend it.