Oahu honeymoon

Hi there!

My fiance and I are getting married in September, and debating whether to take our honeymoon in mid/late September, or early October. We’ve pretty confidently decided on Hawaii at this point (primarily looking at Oahu). Has anyone honeymooned there before that has tips/tricks for us? Places to stay, flights, best/cheapest way to get between islands? We’re hoping to stay within a roughly $3,000 budget as US residents