It's funny you bring this up because I am leaving on Monday for my 3rd trip to Hawaii with small children. The first time, my oldest was 2. The second time, my oldest was 4 and youngest was 10 months. This time, my oldest is 5 and youngest is 2. I understand people suggesting you wait for the luxury vacation, but your life is now. Who is to say what the future will bring! If you have the means and the desire for a trip to Hawaii, or anywhere else you'd like to go, then I say do it! And for the record, my oldest does remember Hawaii. She is so excited to go again, it's all she's talked about for weeks! I have been to Hawaii several times before having kids, so I will also tell you it is like a different place when you bring them. I see things there I never would have noticed before if it weren't for my kids...through the eyes of a child. : )
As for the long flight, both of my kids handle it well. We bring a DVD player, so they sit and watch movies. We also bring coloring, puzzles, etc. The plane is huge so you can get them up and walk them around without a problem. They love looking out the windows!
Finally, when our youngest was 10 mos, we took her as a lap child. It was not a big deal to us. My hubby and I took turns holding her. Also, on both flights going and coming, the attendants actually moved people out of our row so we could have an extra seat. They can be very accommodating when you are traveling with small children. We were able to put her in the extra seat for feeding, diaper changes, etc. We also laid her down in it for naps (keeping an arm around her so she was secure). If you prefer the 1 year old for sure has a separate seat, you can always purchase one and put the child in it in a car seat. There are many ways to make it work.
At the end of the day, we have always believed you live life as it comes. If Hawaii is in the cards for you today, don't let kids stop you from going. Embrace the opportunity to do this with them. Even if they don't remember details of the trip, the bonding experiences you will share will always be there. Feel free to message me if you are looking at going and would like any other tips on travel, family friendly hotels, activities, etc. Happy to help! Have fun!