My husband and I are planning a 2-week trip to Hawaii next year and need advice on when to visit. We want to see and do as much as possible and are considering Oahu for 3 days, Maui for 5 days and the remainder on Kauai.

Suggestions anyone? Any specific pros/cons to Feb, May, Sept.?

Also, has anyone used Priceline.com for accommodations?

I was in Kauai in late September and it was perfect! It's the only time I've been there so I don't have a basis of comparison. I would avoid the summers for sure...probably too hot and humid.

I'd opt for February so I could be there the same time as the whales love to visit!

If you like cold weather go in February

We went to kauai and oahu this past February. The weather was perfect during our stay.

Went to maui in late January. Rainy, cold, and strong trade winds. Too cold to go in the pool.

Too bad you are leaving out the Big Island, as that means you don't care to see an active volcanic eruption..quite a sight to miss when you have traveled so far.
Whales in Feb is certainly an incentive, as that is another real trip! Late Sept would be my alternate recommendation. After living there 10 years, I found the most unreliable weather is May..I had many residents agree with me.
It can rain anytime, but generally you can drive to a different part of the island & find sun..however, that is not always true & especially on Kauai.
Hope your trip is perfect, and anytime in Hawaii is better than other times most places. Aloha, Linda

This web site gives you Hawaii weather by month.

http://hawaiiweathertoday.com/mwt/mwt_wxmonth.html

We spent our family vacation on the big island and maui this past Feb. The weather was great and seeing the whales was one of the most spectacular things that we have ever seen. We were able to see them from the shores of both the big island and Maui. I would highly recommend it. I will say that the water temp is a little cooler in Feb than any other time of the year but not a great difference. The water temp is still around 75% in Feb and we had no problem snorkeling.