What to do in Honolulu?

Hi there, we're planning a trip to Honolulu in April! I'm so excited, it'll be our first time in Hawaii. We'll be staying in Waikiki, with our 3.5 yr old and 1.5 yr old. I'll also be about 27 weeks pregnant 😆 Anyone have suggestions on what we should do or where we should visit? I'm not planning on renting a car right now.