We did not take a tour in Honolulu...we have been there before. On this voyage we decided to walk around Honolulu and Waikiki. Honolulu is nothing but Los Angeles (we live in L.A.) on an island. There is traffic, homeless, and graffiti. Waikiki is nothing special anymore...it is more like MIami...lots of upscale stores interspersed with bums sleeping on the sidewalk. The famous beach itself is really nothing special...there are dozens of other beaches in Hawaii and California that are much better. Our walk around the area was quite eye-opening...when you are on a bus, one doesn't realize how dirty the city has become.
Hilo is an interesting city to walk around. The farmer's market is quite interesting to see...fruits and other items that are not available anywhere else but in Hawaii. The old part of town is small and easy to tour on foot. There is an Tsunami Museum in town, but admission is required ($8). To us it was a little too high for what you get.
Even though Lahaina is touristy, it is still fun to walk up and down the street...there's lots of people and lots of interesting shops. However, one should not stop walking at the edge of the shopping area...keep going into the neighborhoods to get a feel of how it would be to live there.
The Wailua river is a little over-rated. It is beautiful, of course, but please be aware that the river looks the same all along the whole ride. The scenery doesn't change. In other words, after one has seen the river for about five to ten minutes...that's it! Our tour lasted about 45 minutes each way and I was done with it after ten minutes, Fortunately, they had superb hula dancing performed by beautiful women on our boat which made up for the slow ride.