Where should we live??

Hi,
Have you visited Fiji before? I'm not a surfer, so not sure what ideal conditions are. But Denarau is incredibly expensive and there are no options to surf there. It's just an island with 5 star hotels and a marina, unless you have a big budget for rent and living expenses. If you want to live near Denarau then you are better off in Nadi. More affordable accomodation options and super markets etc. Denarau is basically in Nadi, so no difference there. Coral coast is all reef platforms before the surf breaks, so providing you can go out and surf on the edge of the reef that's an option, the main town is Sigatoka, which has all you need or Korolevu if you live further down the coast. Pacific harbour may be an option for you. Big expat community, 45 mins from Suva and a nice beach area. If you stay in Nadi, natadola is not far and I believe people surf there.
Are you wanting to put your children in school? If you do not want to live in Nadi or Suva, you will need to look into public schooling for your kids. My sister attended a village school in Suva rather than an international or a private school.
If you haven't visited Fiji before, go over and check it out first to see the area you pick has the best options available to you for your purpose.
Good luck!