I loved the Full Moon Party, but once was enough. Afterwards I'd prefer to stay somewhere a bit more quiet and Haad Rin Beaches are all about parties. So if you don't mind staying up late, constant noise, music, drinking etc - you're going to love this area!
The Big Island is simply amazing. I highly recommend a helicopter ride over the volcano and riding horses at Parker Ranch. I love that the island encompasses all climates... humid, dry, wet and cold. And if you are a coffee lover like me... Kona coffee is the real deal. I've been to all the Hawaiian Island and enjoy them all ... but the Big Island has a very big piece of my heart.
Proabably worth it if you get on time to dig for the hot water (2h adjacent to the low tide). Otherwise, there are nicer beaches in the area. The beach looks like bombs exploded all over due to everyone digging everywhere.