Kauai | so many times
Growing up in San Diego, we didn't travel much because my parents (being from Canada and Pennsylvania) felt we already lived in paradise, so why bother leaving?
It wasn't until my honeymoon in 1995 that I finally went to Hawaii. Well, IT is paradise. and now, my husband, family and friends been back nearly every year for the last 13 years or so - it's like a second home. We love it so much.
I'm a creature of habit when it comes to Kauai. I like to shop at the same places, swim at the same beaches and hopefully eat at a few new restaurants along the way. So not an itinerary here, but a jumble of places and things and beaches that we always do - hope this helps!
Also there is a great book called Kauai Underground Guide that was our bible for the first few trips. Highly recommended.
As soon as we land and jump into our rental car, it's straight to the Star Market at the Kukui Grove shopping Center (which I see now is permanently closed). So you can head to whatever grocery store replaced it or the Safeway In Kapaa, which is open 24-hours.
The beach at the Hyatt is not swim-able, but right down the road is Poipu beach park - and a restaurant we always eat at called Brenneke's brenneckes.com. Food is just ok but the view is amazing, and it's open for lunch and dinner. Snorkeling is ok at Poipu (not great) but if you like to boogie board and are a strong swimmer, about 100 yards to the left of Brenneke's is a small beach with great waves for boogie boarding (called Brenneke's beach, I think). Poipu has a large beach park, with a kids beach and BBQ areas. Not alot of shade, so bring a hat.
Further down the road (west) is a restaurant called The Beach House the-beach-house.com on Lawai beach. This is an amazing restaurant for dinner and a great place to snorkel. The shave ice cart across the street from the beach is the best on the island. Possibly better snorkeling at this beach and a really nice patch of grass outside the restaurant for reading a book and looking for sea turtles.
The Marriott marriott.com at Kalapaki beach has a fun place on the beach for lunch called Duke's Canoe Club dukeskauai.com, it's a chain from Maui. That beach is nice (no shade) and we have a tradition of going to lunch then spending an afternoon floating past the breakers or taking a surf lesson, but no protected cove for snorkeling.
We don't spend much time in Kapa'a but the book covers restaurants/beaches there. Don't go to the Bull Shed, it's over-rated.
CRITICAL: The farmer's market on Friday at 3 pm in the Lihue high school parking lot is fun - they sell a lot of island fruit, leis. Bring your own bags!
Koloa has a Farmer's Market Monday at noon. Check the internet for the full list of Farmer's Market times and locations - they literally never change, but it's good to confirm because they are really the only place you can buy local tropical fruit, which is one of the main reasons we go to Hawaii. Gotta have it.
If you like granola, look in the grocery stores for a brand called Anahola Granola. It's so good and we not only bring it home but order it online during the year.
Up north there is good snorkeling at Tunnels beach, down the YMCA camp road on the right side of the road outside Hanalei. Really interesting to swim thru the lava tunnels, but also a little scary.
Our favorite beach is at the very end of the road in the national park, called Ke'e beach. We've started going up in the afternoon, staying for sunset and having dinner in Hanalei. Last year we swam with turtles at least twice there. You have to swim out past the reef to see them.
In Hanalei there is a sushi place on the second floor of the strip mall, very casual. Also there is a shave ice place in Hanalei, and several restaurants, including the iconic Bubba Burger.
Other activities we have done include the river kayak trip - WAY too much paddling (it's a vacation). There is a cool big catamaran that sails from near Lawai beach and that is fun, and often you will sail with dolphins. We have taken ATVs around a old sugar cane plantation and driven east to the end of the road where the trail to the Napali Coast begins (or ends, depending on what direction you hike). Really, the most amazing thing is taking a helicopter around the island. It's an expense, but you can't really see the island on the roads, since there are many places on the island that are impassable. One of the best things I've done in my life, it's worth it!