There are various island nights to choose from, a lot of the big resorts put them on as well. The Staircase island night is one of the cheaper options. It includes transportation there and back and there is the option to have dinner there as well. Apparently the dinner is quite good, but not traditional food.
The show started about 9 o'clock giving us time to grab a drink and table. The dancers bounded into the bar, swinging their hips to the traditional beat of the drum. The first group were all girls, dressed in, I'm not kidding, coconut bras and grass skirts. Lets just say they had the attention of all the guys in the room. They were followed by a three young guys wearing not much more. And the two groups alternated for the rest of the show doing traditional dances.
I have no idea how authentic the show was, but it was certainly good entertainment, culminating in sheer comedy. At the end of the show the dancers invited members of the audience up to dance with them, perhaps getting a bit of revenge on the tourists. Watching middle aged western men who generally aren't the best of dancers attempt to keep up with a grass-skirt hip-rattling Raro dancer is one of the funniest things I've seen in a long time. And if you find you've been inspired, after the show there's a bit of a disco with slightly more modern music (be prepared for Michael Jackson and Abba!)