Our two most favored beach locations on Kauai are Shipwreck's beach on Kauai's south shore, and Hanalei Bay and the north shore. Both of these beaches offer many scenic picture opportunities for getting married with turquoise blue ocean and cliffs or mountains in the background. Both locations are easily accessible for your wedding party with parking available close by and only a short walk to the beach. Both locations also provide large beaches so you can accommodate groups of up to 30 people easily.
Shipwreck's beach has the advantage that there are also a couple of fabulous restaurants available right at the beach, or close by. Tidepools, which is part of the Grand Hyatt Kauai, offers wonderful local cuisine in a beautiful setting that's hard to beat for a romantic wedding dinner. The Beach House, just a short 5 minute drive away delivers great atmosphere paired with delicious food, but is a little more busy but fun.
Anini Beach on Kauai's north shore deserves a mention because it's quaint and calm and gorgeous, but it's only suited to small groups of 15 or less people because there's little parking available. The same is true for Tunnels Beach on the north shore. Parking is impossible with police out ticketing folks but the backdrop to your wedding photos is truly stunning and unmatched.
Kauai's east shore offers beaches that are more off the beaten path and may be a good choice if you're staying on that side of the island.
Of course there are other venues than the beach, but all of them are on private land, like a hotel or a botanical garden, and site fees can be quite expensive. However, if you're not swayed by the high price ticket these venues come with seating, privacy, and maybe an arbor under which to get married. Site fees alone can range from $2,000 to $5,000 and higher, and do not include the wedding itself, photos or other extras.