kauai hop on hop off?

Is there a hop on hop off type bus in Kauai?

No!

When we were in Kauai we took a helicoptor tour with Blue Hawaiian and then we met with Jay Dorrance of Tread Lightly Kauai. There is a website. I don't know if this would interest you, but he will do a custom tour just for your party. We drove around with him all day and he took us to places we said we'd like to see (including an emergency stop at a drugstore and a Starbucks :)). We did some hiking and saw some falls and other things.