The dining options in Kailua-Kona are not spectacular, especially if you are coming from a big city like New York City. We tried this place called Sibu Cafe, and we found this simple cafe to offer nice and light Indonesian Fare. It's not a romantic setting there in the courtyard of a small shopping center, but the food tasted authentic and just what I needed after all the fried SPAM I had for lunch.
I recommend the green vegetable curry and the beef satay, but you won't be overwhelmed. Tastes more like home cooking. It closes around 10 PM, like most of Kona does, so get there relatively early. It will be a nice walk in the touristy town, if you go along the harbor after dinner.