We visited in December of 2010. But I have memories of this place from the early '80s! I also miss the show with the Hawaiian princess, but I'm sure you can imagine that left quite an impression on me as a little girl. In 2010 I took my three little girls here and we splurged on a Dolphin experience. We did the milder (and cheaper) Dolphin Encounter, as my kids were just 3, 6 and 9. This was perfect for us. We all loved it. We also stayed for the show and toured around the park. We also bough the professional pictures because we will probably not do this again and the photos were worth it to me. Plus, other visitors NOT doing the experience cannot get close enough to take good shots.
At least according to my research at the time, this is the most affordable dolphin experience. It is much more expensive at the hotels and other venues I found. You do need to get there, which adds time and travel cost. But because I wanted to return to this childhood memory of mine, that cost was worth it to me. Plus, we are familiar with the area, so the travel was not stressful. It's pretty easy to get to. I would plan around city traffic times, though, if you are coming from the leeward side.
Now, if you are NOT doing an experience of some kind (feeding, swim, encounter, etc), then there is not too much more to do here. Still, it would be great for kids who love animals and great for families who would like more appreciation for the wildlife treasures of Hawaii. The show was fun, but similar to what you might find elsewhere - except where else can you see a Wholphin?!
Finally, this is NOT like Sea World. It is not HUGE and full of rides and killer whales. There are not lots of other activities to keep you busy from open til close. I would suggest building a visit around a dolphin/shark/feeding experience, getting there early to take in the other exhibits and planning on about half a day. We ended with some ice cream and all left happy!