Mt wife & I stayed at Matanivusi last year. It is on the Coral Coast about half way between Nadi & Suva.
surfingfiji.com/They have sole access to 4 breaks out the front of the resort as well as Frigates which would be doable on a SUP when small. Frigates is about 40 mins away however that is in the 20ft Noosa Cat with twin 200s (not a longboat with a 40hp) & a top way to turn up to the break!!
Great resort run by an Aussie couple with only 12 guests at max. Take a short-board as well.