Ouvéa — Is a long narrow spit of land on the crest of edge of an Atoll with long white beaches (25km) of turquoise water which are quite breathtaking.
Lifou — The most populous of the three islands. Cruise ships often stop here in the Tribu/provence of Easo for a day excursion.
Tiga — Smallest of the Islands, day trips are possible from Lifou, but you need to go to the Marina to ask if a boat is going, if there is not enough people it does not run. I don't think there is anywhere to stay but tribal accommodation can be arranged. Try making arrangements through the Tourist office in Lifou.
Maré — Allegedly the population is declining and has limited infrastructure to support tourism. Don't let that stop you as this place is what you would expect from a tropical paradise, surround by coral with great snorkelling to be had all over the south west of the islands. It is also known for its great sink holes, although it would be advisable to get a guide to take you there.
With out some basic understanding of the French Language its makes it difficult to get around on any of the Islands.
Apparently some Japanese is spoken according to signs at the Airport in Ouvea and Lifou.
Local dialects on the Islands are different with some commonality between Lifou and Mare, but not in Ouvea.
Generally a hire care is a good option, Lifou and Mare have hire cars at the Airport although a car be hired from other vendors and organised to meet you at the Airport and be dropped off at the Airport
Ouvéa — Taxi - There is only one Taxi on the Island, driven by Rogez +687 797202 he can pick you from the Airport and also give you a day tour.
The islands' beautiful water is prime for snorkeling and swimming. Jinek Bay, a natural marine reserve, along with Jokin Bay on the northern shore of Lifou are stunning in their coral and marine life including sea turtles.
On the Islands various accommodation is available ranging from Hotels, Gites, Tribal accommodation and camping. Most Gites, which are bungalows run by local tribes offer a camping option. Dinner at the Gites and camping is best organised in the morning so that they can cater for you.
Ouvéa — Camp de Lekiny, This is camp ground, meals about 900 CFP and the have beer camping is about 1000CFP per night per person, 1500CFP per night for two persons. Tents can be hired there. They also operate a dive boat and glass bottom boats
Tiga — Only tribal accommodation is theoretically available, best try to organise via the Tourist office in Lifou.
Maré — Negohene Village a 3 star hotel nestled in a forest on the side of a reef, with immaculate gardens. For its price ~15000CFP night I think it completely reasonable for your own bungalow. There is a Gite in Wabo not from from Neoghene village (more information required)