Nadi area - August 08

Me and 3 friends will be stopping in Fiji at the start of august 2008 for 3 nights, on our way from australia to the USA, we will probably just stay in the Nadi area, but i had looked at the possibility of spending a couple of nights on one of the Islands in the Mamanuca, we want to do it as cheap as possible,

are there any specific islands anyone would recommend? should we just stay in the big dorms on the island or spend a wee bit more money for a couple of the Bures for a couple of nights, any recommendations or advice would be great thanks

Oh, and another thing... should we book in advance? or would it be ok to arrive in Nadi Airport, and just try and get somewhere to stay then?

Not much to see around Nadi an island would be better maybe Beachcomber which has a dorm and is all inclusive.
Probably ok to book on arrival in Nadi.
Depending on your arrival time in Nadi you probably need the first night there and go to an island the next day.