As a former resident of Oahu, yes, your concerns are real. The most common places years ago for break-ins were at Pearl Harbor, Waikiki, and Polynesian Cultural Center (where our car was broken into).
If you pack the trunk BEFORE leaving, have nothing visible, then you are likely okay. If you open your trunk at your destination for any reason, make sure there is nothing in it. They have gangs watching.
I do agree, you don't need a car at Waikiki. Our next trip, we're 5 nights Waikiki then a week at Ko Olina. I just booked an SUV from the airport for the week; we'll Uber, Lyft or taxi to Waikiki, as parking at our hotel is $45/night (plus tax, and we won't use the car while there, so saves that plus the extra $250 rental). Waikiki is walkable, and we really don't plan on doing much touring (we lived there so been there, done that, but if we did tour we'd hire, take a bus, take a taxi, etc). You can really get by without a car in Waikiki.
If possible, the day you move hotels, I'd get the luggage to the new hotel and have bell services hold it safely.