We have found this website to be extremely helpful in planning our Hawaii trip!
https://thehawaiivacationguide.com/oahu-travel-guide/
They also have a youtube channel!
https://www.youtube.com/playlist?list=PLAtd_s8w8KUVsUxxdj2OtM-ZUyvZr-12O
Please check them out, as they truly answer so many questions and have excellent recommendations on what to do around Oahu and the other islands as well!