6 Days in Fiji

Hi

I am off to Fiji in late August with my partner. We could only get 6 days off work, so we are thinking of splitting this into 3 nights on the main island and 3 nights on a smaller one (e.g. in the Yasawas, but it doesn't have to be there). Does anyone have any suggestions as to where to stay on Viti Levu and on the Yasawas or other offshore islands? (We are not looking to 'rough it'). We're keen to do a bit of exploring, e.g. of the hills, local culture etc on the mainland; but want to combine this with time on an amazing beach in a decent hotel with good swimming and snorkelling.

Any advice would be much appreciated.

Hoj