If you have never been to Hawaii before, be sure you know what you want to see and which islands you want to visit. We have been to Hawaii several times, so when we did our
DVC exchange, we knew we wanted either Kauai, Hawaii, or Maui. We usually start and end our trips on Oahu (Honolulu/Waikiki), so we knew we didn't want a whole week there. If this is a first trip, I would recommend a few days on Oahu to aclimate and see the historic sights there, and maybe the Polynesian Cultural Center etc. Then I would choose the one other island you are most anxious to see, and spend your week exchange there.
We did two exchanges, so 1 week on the Big Island of Hawaii from our DVC, and 1 week on Kauai on our friend's gold Crown resort exchange.
We really like the Big Island of Hawaii, but Maui and Kauai are a very close second for us, with no real preference. If you are golfers, Maui has an edge. Kaui and Hawaii are the most laid back and relaxing, and Maui has the best of both worlds and is a little more upscale. Oahu is really a big city and not so relaxing, but has lots to do. If you want to see volcanos, you have to hit Hawaii. Some like to take day trips to the outer islands, but that is a hectic day with flights etc.