1. How old are your children?
2. Do they enjoy eating out at restaurants?
3. Does your family enjoy bbq type food (ribs, grilled saucy chicken?)
4. Does your family prefer New American/ Fusion cuisine?
5. Have you ever seen a Polynesian dinner show/ luau type show before?
6. Is someone in your family really "into" tropical/luau type stuff?
Kona is very nice. Its a bit overrated on the DIS, IMHO. Why? I think because...
a) The Menu: it isn't all that, but its got the reputation for being SO creative. Kona does have a nice, well-considered, asian-american fusion cuisine menu. It might be much more creative than you are accustomed to normally and therefore the menu will be exciting for you. We have a couple of great restaurants with a similar culinary approach in our home area, and we like that kind of food a lot, so the menu was appealing to us but not *exciting*. I am not being a snob here; until a couple of years ago we didn't have asian/fusion restaurants near where we lived and we found them much more exciting to try when we traveled because of that. As that style has become more widely used, I think that the Kona menu loses some excitement, for us. In contrast to other Disney resort offerings-- well, yes, Kona's menu might well be considered very exciting. But we personally found the choices at World Showcase more exciting simply because, for instance, we have never had the chance to try a Moroccan restaurant before-- so that was more exciting. It did not turn out to have better food than Kona, but I am glad that we did both, and if I had to eliminate one, I'd rather have kept Morocco simply because that is not something I can get at home. Fish crusted in macadamia nuts, while LOVELY, is on a lot of menus here at home.
b) The Service: We had FABULOUS service when we were there, but the table next to us had terrible service! We noticed the difference while we were dining. Their server let their drinks run out, they sat at least 10 minutes earlier than we did and their food came SIGNIFICANTLY later (and not because they had well done steak, either.) And their server gave them a hadr time about getting their desserts to go. (They heard us order ours to go when our food was brought to us because we were in a hurry to go see the water pageant on the beach and felt that, since we would be too full right away anyway, it would be faster and more fun to take our desserts with us to have picnic style or save for later.) Our server thought our to go idea was great and she very thoughtfully suggested what would go "to go" best and was lovely about it. Their server was a snot about it. My point is that you can get bad or good service at any time, anywhere. Generally, all the service at Disney World resort is very good. But I wouldn't book a restaurant because someone had a perfect waiter there one night and posted about it.
c) The Location/ Atmosphere: We stayed at the Polynesian, and loved it, but the Kona Cafe is the least atmospheric of the dining choices. This is not destination theming-- this is a hotel restaurant, and its very nicely decorated, but its not the "jewel" of the resort. The theming of Ohana is nicer as is Luau Cove. I get the definite feeling at Kona that this restaurant was planned primarily for hotel guests and not as a "destination" restaurant. It is set up similarly to a lot of other hotel "cafes" I have eaten at-- it is completely open to the lobby area of the hotel. That said, it is very comfortable and quite nice.
d) The Food: was great. It really was, and the portion sizes were very appropriate, and the food was prepared well, presented very well, and tasted great. We really liked it, all of us, and found some of the dishes to be on our "favorites" list from our week at Disney-- the crabcakes! They are special. I personally disagree with posters who call it 5 star, or compare it as an equivalent to California Grill or Citricos or other fine dining hotel restaurants (its not, say, Emerils' Delmonico or Tao at the Venetian in Vegas-- those being two really exceptional dining experiences we have had recently, whereas California Grill definitely matched that level.) But it was very good, and better than any theme park restaurant we ate in. I liked how light everything was.
e) Child Friendliness: nothing special to see or do for our DD4. It was like taking her to any other nice restaurant at home with concurrent fun and aggravations. But both Ohana and the Luau offered a LOT for her to see and do and be engaged with beyond her plate and some crayons. NOW, I don't mean to say that every meal needs to be chock full of entertainment-- but if that is what you want, its not here at Kona. That was a good thing for us when we ate there because we were burned out on all the action at the character meals and dinner shows we had attended up to that point.
OK-- we went to the Luau, and we LOVED it. No, the food is not super stellar. Its good enough, you get a lot, and they bring it promptly. We liked how festive the Luau was. It was very different from anything we have done at home and different from anything else we had done at Disney that week. The show *is* corny, but my daughter found all the colorful action engaging... until she fell asleep

. But up to that point, she really loved it and she still talks about it.
My understanding is that the Luau at Disney can't really compare with what you can get elsewhere as Luaus go-- but since we have no basis of comparison (no Polynesian theme places near us and we have never traveled to Hawaii) we liked it. We also found the dinner show format really really relaxing. Until DD fell asleep (it was a little late for her, the second show), she was enjoying herself and we had nice family time without the pressure of jumping up to do a coconut race and take a picture with a character (fun things to do, of course, but this was late in the week and we were ready to relax!), after she fell asleep DH and I just relaxed and drank our admittedly not-great but constantly refilled wine and beer, rolled our eyes at the corny jokes, and videotaped the firedancer for DD to watch at home.
It *is* a little pricey that it is 2 TS. It was worthwhile for us because we knew we didn't want to eat all that many sit-down TS meals anyway-- so we didn't mind burning some credits off there, and needing to pay oop for a dinner another time, because we knew that OOP dinner would most likely be a CS anyway, and not terribly expensive for us (my DD4 and I often shared things.)
ALL that said-- the Luau might not be ideal if you think you might want to go back to the MK for fireworks on your last night, and you don't get a good view of the fireworks during the show if you attend the second seating (you can see them from some seats if you try-- but the show is going on, and that is the focus then.) On your last night I am a BIG fan of no ADRs and just having some portable food as you catch your favorites one last time.
have fun!