Out of the hotels you listed, we've been to the Grand Hyatt in Kauai. The resort is perfect for a 9-year-old. The pool has a lazy river and pool slide, and there's also a lagoon where you can rent kayaks. On weekends, at the Seaview Terrace (a lounge area that opens up to the Pacific Ocean), there's entertainment with hula dancers and live Hawaiian music. There's lei making and shell necklace making activities for kids. We had a great time at this resort. Also, customer service was great. We loved it there.
The only thing is that Kauai is a very quiet island. There's no active night life, shopping malls, or a huge selection of restaurants to choose from. The activities outside the resort are very outdoorsy (like hiking at the Waimea Canyon), which my DH loves. We were unable to snorkel from the beach (Shipwreck Beach) in front of the Grand Hyatt because it's too rough. You also have to make sure you go at a good time of year when it doesn't pour rain. (It's a lush island and is known as the garden isle for a reason.) If you like more of a vibe and energy, then Kauai may be a bit too quiet. We loved Kauai, because we went there to get away from it all. Our kids were 6 & 9 when we went, and we had some amazing family time.
Now that our kids older, we go to Maui and Honolulu, because our tween and teen love the energy and vibrancy of both. But whenever we go to Maui or Honolulu, I always wish we were at the Grand Hyatt instead. It is the perfect resort IMO.
BTW, I've never stayed at the Kaanapali Beach Hotel but have passed by it. As a resort, it does not compare at all to the Grand Hyatt.