There are four recommendations we have for you on Oahu: Waikiki, Pearl Harbor, Hanauma Bay and the Polynesian Cultural Center.
Pearl Harbor https://1000fights.com/remembering-pearl-harbor/
Located a few miles, but light years away from the hustle and bustle of the city is Hanauma State Park (https://hanaumabaystatepark.com/).
You can dive at the many reefs along the north and south shores, take a helicopter ride to waterfall spot, hike into a secret beach, play a round of golf, or do absolutely nothing sitting on the beach.
If you are looking for a cross between the hustle and bustle of Oahu and sleepy Kauai, Maui is the place for you.