If you are in Nadi for a few nights I can highly recommend Sonaisali Island resort.
It's about 15mins by taxi from Nadi itself and is a 105 acre island about 300m off the coast reached by boat that they have staff at 24hours a day.
It's a good base to have a few days to unwind and have an island feel while still being able to pop into Nadi during / hire a car (if you do hire a vehicle on the mainland I'd recommend a 4wd as once you get off the main road it's pretty rough dirt roads in a lot of places)
http://www.sonaisali.com