This is a good point. Our two nights on Oahu were spent on Waikiki ... The Pearl Harbor visit was obviously the highlight of that part of the trip (and perhaps the entire trip), but I see bringing the kids back to that after another 10 years or so. I want them to really remember that and feel the emotion. Other than Pearl Harbor, I could probably leave the rest of Waikiki. So maybe no need for additional time there.
Since we are doing a week at Aulani, we can spend some time doing some other things on Oahu without staying elsewhere anyway.
After these first several comments I'm thinking more Maui vs. Big Island, and leaning Big Island just because it is new to us and there are so many unique things to see. We like the national parks a lot, and Haleakala was a highlight for us last time. It was a beautiful clear day, and we could see the peaks of Mauna Loa & Mauna Kea in the distance (not sure how common that is, but it was sure memorable for us). We also have a family friend that has something like 3-4 weeks of Hilton Grand Vacations points on the Big Island, and I think we could rent a few from them at a discounted rate. So that may tilt the scales as well.