We have been vacationing in Kauai since 1995 and have been to all parts of the island. The Poipu Beach area quickly became our favorite spot. I am retired and do a fair amount of traveling. If you enjoy serious hiking, Kokee Park has some awesome trails on the South side of the Island, and in the North you will find the famous Kalalau Trail.
We have found the Poipu Sands complex to be very quiet. A good place to recharge your batteries.