We did 12 hours from Chicago to Maui direct, it's long and boring but at least you know when you get off the plane, you're there. As long as you move around and stretch, and bring plenty to entertain you (and snacks), it won't be as bad as it sounds!
I am SO jealous of this trip, I can't wait to hear all about it. My husband and I are dreaming of the day our kids are old enough to take to Australia - before kids we had to choose between Australia and Hawaii, and went with Hawaii. Now that Aulani is here, I wish we had done it the other way, we could do Hawaii with kids!