We just got back a couple weeks ago from first time visit... Didn't bring our kids tho. ( All in college )
Dole Plantation. It has a train ride, maze, and garden you can walk thru. We thought train ride was fun ... Other 2 we wouldn't do again.
We used an app called gypsy guide. It was pretty good... I think it was around $15 for the island of oahu tour. The app uses GPS waypoints to play audio as you drive around the island... We saw a bunch of things we otherwise would not have found. ( Punchbowl crater, a bunch of scenic lookouts, some turtle beach, a temple, waterfall, a windy Lookout over Waikiki etc...)
We didn't do the Polynesian Cultural Center. There are posts about it. Some seem to love it some seem to hate it. Could be an option!
We wanted to do the ranch, but didn't make reservations before we left... So missed out. They have a bunch of tour options. Can't speak to any of them personally, but lots of posts on that too.
Have fun!