In order of favorite, as ranked by the kids…
Kalihiwai: We can’t stress enough that while this is a great beach, it is one of the few places that tourists really have not managed to find. So we try not to make a big footprint here. Directions from Princeville travelling south: Turn left on the second Kalihiwai Road; then take an immediate left and follow the road all the way to the bottom. We strongly advise you to continue to the end of the road by the stream and park under the trees. There are picnic tables there. and the stream is a great little place for the Keiki to play.
Hanalei Pier: Or Black Pot Beach Park is a great place to spend the day, and it’s close to Hanalei town in case you want to grab a snack or lunch. There can sometimes be a good learning wave here, and there will always be a local renting soft boards or giving lessons if you want to give surfing a try.
Lydgate Beach Park: If you have toddlers or Keiki that are not super water-savvy and you want to see some fish, this is the beach for you. There are two man-made protected areas for small kids and bigger kids. Plus, there’s a large playground, and a lifeguard is always on duty at this beach.
Ke’e Beach: This is a great snorkeling beach, located at the very end of the road–just turn right out of Princeville and go until the road ends. Be sure to pack lunch and drinks for the day, since there are no eating establishments nearby. The Kalalau Trail starts here. You must obtain a permit to be able to access this beach or parking area. You can read the requirements on the state parks division website https://dlnr.hawaii.gov/dsp/parks/kauai/haena-state-park/ and purchase permits at https://gohaena.com/ You can reserve as much as a month ahead of time and you better as it sells out quickly.
Take a trip to the west side and visit Waimea Canyon. Make a stop at Kauai Cookies on the way and pick up some locally baked cookies.
Tubing the ditch. About a 3 mile trip down the old sugar cane ditches. Check out the you tube video.