Which island/islands should we visit in 3.5 weeks???

Hi All~
My husband and I are going to be in Fiji for 5 days (after diving with the whales in Tonga for 1 week). We are mainly interested in scuba diving , exploring the culture, relaxing on white sand beaches and hiking. We would definitely like to stay away from really resort-y places. We would, ideally, like to pay around 50$F a night, but could pay up to 100$F a night, preference is aircon or fans if possible, cold water=totally fine. What island should we go to for an experience like this? (We were thinking Nananu-I-Ra, Yasawa, Kadavu, Lomaiviti, Vanua or Taveuni). Any suggestions? Shall we just go to one island, or do we have enough time to island hop? After recommending an island, can you recommend a dive shop on that island? We are a bit behind the proverbial eight ball in planning this, as you can probably tell, so any suggestions would be GREAT! Thanks!!!! ~Dani

Oh yeah, and we don't really care about nightlife at all....actually, we would kind of like to avoid it. ~D

This is confusing, you post this in the subject line

"Which island/islands should we visit in 3.5 weeks???"

Then later you say

"My husband and I are going to be in Fiji for 5 days "

Which is it 3.5 weeks or 5 days?

You won't get air-con for even F$100. If it's a five-day trip, pick one place and stay there. If it's 3.5 weeks, that's a whole other ball game.