'Ohana and Kona are very different.
First of all, Kona is in the front side of the hotel lobby so you cannot see fireworks (nor does it have any windows). The atmosphere at Kona is almost like a very open Starbucks. It is true to its name--it is a cafe and it kind of sits out open in the lobby. To me, that is it's only drawback. The food there is very good. I wouldn't say that it has the quality of Artist Point or Citricos but it is also cheaper. Still, the food quality there is VERY good.
'Ohana is a "fun" place. It has a better ambience becuase it is an actual, enclosed restaurant. If your kids do not like the typical fare at 'Ohana, they can bring you a plate of chicken tenders.
I prefer Kona to 'Ohana but my kids are older now and I'm sort of past the "fun and games" stage for dining. I do think that everyone should try 'Ohana once despite the fact that I'm not crazy about the quality of the meat. (love the platters though with all the little stuff on it).