If your idea of a good holiday is looking for bars heaving with others from your own nation and having a loud, drunken time, go somewhere else in the world. Nightlife in the islands is what you make it. Rarotonga has plenty of places to go, but it's no Ibiza, Sydney or LA (thank goodness).
If you're going to the outer islands, you will have to ask the locals but don't be suprised if, they suggest joining in the bingo night at the local church hall! People make their own entertainment and it's a long long way from anything in a big city. I had some great nights in Mauke just chatting to the locals.