I'd say enjoy a weekend in the city (Honolulu/Waikiki) and be like a local. Hang out at Ala Moana beach park where you can SUP/swim/grill on one of the public grills, eat your way through Kapiolani Community College farmers market, have dinner at Shabu Shabu house, happy hour at Rum Fire in the Sheraton, watch the Aggies at Giovanni Pastrami's (Oahu A&M club usually meets there, check FB page to verify), eat dinner at Lucky Belly in China Town, hike Diamond Head, rent a bike and ride the 'Lei of Parks', surf Waikiki, etc.
I lived on Oahu for over 4 years, and this is what I'd personally do. North Shore is pretty busy this time of year so I'd avoid it unless you want to watch surf tournaments.
Either way, you'll be in Hawaii and really can't go wrong. Aloha my friend!