I would just bring over say an 8lb spinning reel and buy a cheap rod over there. Once you use the rod, just leave it there. Its not worth the hassle of bringing it back. You can buy rods at Sports Authority, Walmart, Longs, Sears, or a tackle shop. You will be surprised how many places actually carry fishing stuff.
You are dead on about shrimp and squid. Personally I normally got a wider array of fish with shrimp vs squid.
Fishing will be better in Maui vs Oahu. When on Oahu, will you have a rental car? I would assume while you are staying in Oahu you will probably be near waikiki. You can walk to the Ala Moana beach park and fish there. Your wife can be shopping across the street at the Ala Moana shopping center. If you have a rental car and would like to drive. Drive out to the North shore area (from turtle bay area to Hale Ewa, you will pass through Sunset Beach, Bonzai Pipeline, Waimea bay, etc) just stop anywhere and fish. Just a word of caution, the locals tend to prey upon rental cars. Leave your car empty and carry cameras etc...Its a relatively safe area though.
If you do opt for the north shore area try to do it in the morning...The parking lots at like Waimea bay fill up pretty fast.
Pic from the north shore area.
Waimea Bay