I used to live on Oahu, and now go back about every other year or so. We went this summer and last year. If you want any advice once you make your plans, PM me.
I do agree about staying in a condo - we do! At Ko Olina (west Oahu, about 45 minutes from Waikiki) is where we've stayed the past couple of years, and there is a Costco right there, brand new, plus a brand new Target (YEAH! Didn't have Target there before) with groceries. We cooked in every day and ate so well that way. Yes, I probably spent $600 in groceries, but that was for 11 nights for the 4 of us, and we ate out some of course as well. With kids, though, it's nice to go snorkel for the morning, then come in out of the sun, eat a good lunch, take a rest, then go out again as the sun isn't too bright.
Definitely start looking, but I wouldn't buy quite yet, unless you're cashing in miles. My DH flew Hawaiian a couple of times, and he liked them. We always use miles, and come from the East Coast, but you can probably get some good airfares from California. Check out packages as well, but I do highly recommend a condo. Also, take two weeks if you can, and try to see a couple of islands.