With just adults, I would not do Park Faire since that's a character meal.
We ate at both 'Ohana and Kona on our last trip, and we enjoyed both of them enough to put them on our repeat list for our upcoming trip in July. I'd say both have good food and nice atmospheres, but it depends on what you want from your meal.
If you want choices in your meals, close to gourmet presentation, and upscale desserts, go with Kona.
If you want a loud, festive, silly atmosphere with food served family style (and all you can eat), go with 'Ohana.
'Ohana does have activities for kids and entertainment during the meal, so if that matters to you either way, consider it when making your choice. Kona looks like a hip looking coffee shop right off the lobby (some tables are at the railing of the lobby), but the food is better than the atmosphere suggests it will be.