We did not take any tours - but walked the 2-3 miles into town and took the local bus back to the ship. The local bus is free to seniors and if you are looking for WIFI, there is a cafe on the main street that offers it free.
Honolulu is always inviting. Lots of free shuttles as long as you take in a tour of a jewellery factory or go to a shopping area, but they always drop you off in Waikiki and pick you up and take you back to the ship.