We learned to break up the return trip by spending a day or so in either Phoenix or Las Vegas, which are both nice places to spend a couple of days. If it's summertime, then Vegas is your best option unless you like 120 degree weather. That routine also allowed us to get get somewhat back into our normal time zone for the final leg back.
You mentioned you were going to Oahu. That is actually my least favorite island to visit. Honolulu is basically New York City with palm trees. Now as a first time visitor, there will be plenty to do and certainly check out Pearl Harbor and all the memorials as well as Waikiki Beach. You can also get away from the city and get a more Hawaiian experience.
My favorite island is the Big Island and we stay at Kailua-Kona which is the dry side of the island. Rent a car and see the whole island, from tropical rain forests to active volcanoes to ranches that would make you think you are in Oklahoma or Texas. Pretty much every climate (except arctic) can be experienced on the Big Island. But if you really want to see snow in Hawaii, the Big Island is the place to see it if you visit at the right time. Mauna Loa and Mauna Kea sees at least some snow every year. Then you can be back at the 80 degree beaches in an hour or so. Check with your rental car agency though, some of them don't allow you to take their rentals on Saddle Road (which is the way to the interior mountains).
Maui is our second favorite island. The best restaurants and beaches. You can still find your own "private beach" for the day if you know where to look and you can surprise your spouse by going into the ocean naked.
If you want a really quiet experience, try the island of Kauai which has (relatively) minimal commercial development and a lot of open spaces, including a rival to the Grand Canyon.
Anyway, after your Oahu trip, you will definitely want to go back and explore some of those other islands.
Done that. Best is you stay up late the night before and then fly home on the a red eye out of HNL at about 9 pm. Then at least you are zombied out sleeping for half the flight.