If you do Pearl Harbor, get there EARLY and do some research beforehand to figure out what you want to see, or see if there's any way for you to buy tickets from a concierge or something. The way they sell tickets is kind of messed up.
They only allow a set number of people in each day, and tickets go fast, like within the first 30-60 minutes of open. Think of it like a movie theater where you can only buy tickets in person, from 8-9 AM (for example), and your showtime depends on your place in line. If you buy your ticket at 8:00 AM, they'll assign you an early showtime and you'll be home before lunch. If you get your ticket at 8:59 AM (assuming they're not sold out), they'll assign you a 5:00 showtime and you'll either be sitting around for 8 hours or looking for something else to do. Source: went there in June, got my tickets with a shitty showtime, left, came back a few hours later.
Otherwise: Eat a shit ton of malasadas, drink a shit ton of mai tais, and avoid the poor people passing out flyers for WELCOME TO AMERICA COME SHOOT A REAL LIFE FIREARM IN OUR GUN RANGES OMGOMGOMG!!!