Trip to Fiji - Advice Needed

I've already got a 12 day trip to Fiji with my brothers and some friends early next year that takes me to Mango Bay, Robinson Crusoe, Manta Ray, and Waya Lailai - but I'm considering staying on for an extra 7-10 days after they leave to see some more of the sights.

While money isn't a big issue, I'd prefer to stick to backpacker accommodations so I can meet people and spend money on activities etc. Would really love some recommendations for both places that I should stay/visit, and things I should do.

I've got my PADI Open Water cert, so scuba is an option - and I'm already looking at doing a white water rapid tour while at Mango Bay.

Would love some advice!

Regarding accommodations, lots of reviews for places on sites like tripadviser.

Things you should do, really depends on your interests of course.

I'm doing the Upper Navua Gorge tour with Rivers Fiji and am pretty excited about it, although I haven't ever been rafting or in a gorge so it may not be as exciting if you are from an area where things like this are common. Happy to let you know what I think after I do it, just remind me.

Sounds like theres a lot of good diving in Fiji, esp if you are advanced.

I'm looking at doing Upper Navua Gorge too. A tad pricey, but I figure that's why God invented credit cards... >_>

Yes very pricey! I thought it was in FJD and then got sticker shock when I realized it was in USD.

I'm ok with it being US dollars. Our dollar is doing even better atm ;-)