We booked our trips about a year in advance. However, I see you are in CA and you may have more options.
In any case, I would book a soon as possible to guarantee your hotel, flight, car. The authentic luau in Lahania is wonderful and it does fill up fast. If you want to do that, make sure you book it well in advance. Most of the whale watches have availability on the spot and we never had an issue with those. HIGHLY recommended doing this because it was breathtaking to see these beautiful animals.
I book all the personal/business travel for our company and I only go through the airline (American, Southwest) and hotel (Hilton and Marriott) websites. When discounters are used, those are the first to lose a seat or hotel room and you have no customer service to help you... only an 800# and the mercy of whomever you speak with.
For cars... I typically go through Thrifty because we have a corp account with them.. HOWEVER, in the past 6 months, we have used Hotwire twice and both times were a good experience. You pay in advance which sucks so only use them if you know without a doubt you are going. I booked Hotwire yesterday for hubby's regular Houston trip next week and got $97 with all taxes and Thrifty is the company they put us with. Typically, his Thrifty car for HOU trip is $180 for 3 days. So we use Hotwire with caution.... I would never use a discounter for air or hotel.
For Hawaii, we had nonstop to Maui from DFW and we always stayed at Kaanapoli or Kapula. We scheduled trips to leave DFW around 10am and we scheduled the trip home to leave Maui around 10pm so we slept all night and landed around 5:30am at DFW.
We did a lot of dinner, shopping and the base point for whale watching (a MUST DO) from Lahania. We rented a car at the airport. On the way home each time, we stopped by Mama's Fish House in Paia.
Enjoy your trip! It is beautiful.