We had great experience staying at the Shelly's place. It's a bit hard to find the location as the house number seems to be out off sequence. But you'll find it on your right immediately after making the last turn if you follow the Google maps directions.
In our case, Shelly walked out to meet us which was helpful.
Both hosts are great and willing to do extra to make your stay even better. They can give you an advice or borrow some snorkeling equipment depending on what you need.
The room is great: large with a huge closet and a full bathroom. The lanai is awesome and a perfect place to have some coffee in the morning if you wish.
We liked the location very much as most beaches are very close and kona is only a short drive from there.