We are going to Hawaii in March (yay, the countdown is on!). We are 99% sure that this will be our only time travelling there. We will be there for two weeks.
In my original plans, I was considering THREE islands to try to maximize our travels. In reading and researching, I came to realize that this would likely make for a tiring trip (with cranky kids). So, I narrowed it down to two islands - one week on Oahu and one on Maui. I feel like we could have had an enjoyable vacation on one island (there seems to be so much to do on Oahu!) however I had a nagging feeling that I would regret not seeing more. So, we shall see! Honestly, I don't think you can go wrong - it's a vacation to Hawaii!