Heaps of different things, heads up - at Vanuatu there is a turtle sanctuary that you can get via the cruise boat for 150 per person and 100 per child, but If you actually get a taxi yourself - they can take you to another one that costs $50 for the whole family. And you can feed and hold baby turtles.
We decided not to do an organised tour -we hired a cab - he charged us $60 to take us on a sight seeing tour, took us to a traditional village where they did some dancing and singing, then to the Holiday Inn for a swim in the lagoon. And then through town and to the shops.
It really depends what you want to do - I would do some research and decide what you want to do before you go, you can then decide wether you will go with the cruise organised tours (very expensive) or get around yourself, the good thing about Vanuatu is there isn't much crime - well, there is -but not the targeting tourist type.
New Caledonia is different and they say you shouldn't go out at night there. We did the "choo choo" train tour and that was a good way to see the sights, have some apple cider and French Pastries. I think that one was 29 an adult and 15 per child.