Is a day trip to Kauai from Kona enough?

We'll be staying in Kona in March for a week. We were thinking of taking a day and flying over to Kauai while we're there or maybe even leaving a couple days early to hit Kauai first. Do you think 1 full day is enough time in Kauai to do a couple excursions? Or do you think we need to atleast stay overnight 1 night? What is there to do in Kauai? We've been to Maui, Oahu and Kona before and have done the helicopter/plane tours, snorkeling, bus tours, etc.