Kauai - north shore coffee shop
The best espresso coffee drinks on the Northshore at the best price are at Lei Petite Bakery & Coffee Shop in the Princeville Shopping Center. I don't work for any of them, I've tried them all, and Lei Petite is the best. I'm in there every morning.
As a tour kind of thing, on the other side of the island, you might check out the Kauai Coffee Company's visitor center in the middle of their coffee fields, it's the largest coffee plantation in the United States.