Hi, we have never taken a flight with our kids as long as Hawaii (our max flight has been 3 hours) but here is what I do to occupy the kids (and DH usually konks out as soon as we take off, of course I can never sleep on the plane);
* Last prime day at
Amazon I got my 2 kids their own Kindle Fire (the small 7 inch one for a fantastic price), I got the Kindle with a little extra memory as I downloaded a bunch of new movies for them and tv episodes the day before the trip (I made sure to download them as the Wi-Fi has been inconsistent when we fly to the Caribbean and if they are downloaded directly on the device, I don't have to be dependent on the Wi-Fi), prime day is coming up next week, July 12th I believe.
* I get each of my kids one of these bags from Amazon as their carry on;
https://www.amazon.com/Clear-Tote-Z...s&pd_rd_r=70ND97P4T9P0SAY8T09P&_encoding=UTF8
Another vendor makes them in purple;
https://www.amazon.com/Clear-ZIPPER...coding=UTF8&psc=1&refRID=BB4JERGA16AHESQ4KAQX
They are fantastic as they hold my kids device, sweater, snacks, the DK sticker books I buy, headphones, markers, yet they are not bulky at all, they fit right at their feet / under the seat no problem.
* I usually get a cute small art / drawing journal from Michaels and a pack of pip squeaks markers as they color a little. the journals at Michaels have nice covers and come in all sizes, I recently bought this one for DS;
http://www.michaels.com/artists-loft-cork-fashion-journal/10223723.html
* I will get them a DK sticker book, as those are usually their favorite;
https://www.amazon.com/Ultimate-Sti...0944&sr=1-7-catcorr&keywords=dk+sticker+books
My daughter loves the sticker dolly books;
https://www.amazon.com/Sticker-Doll...rd_wg=cBcqT&psc=1&refRID=2VHBHE9X7X1BDDFBXXCN
these are the kids headphones I get (they come in black and pink), they don't go too high as to hurt/damage hearing, they are lightweight, great for travel and my kids love them;
https://www.amazon.com/Sony-Mdr-222...99441531&sr=8-1&keywords=sony+headphones+kids
Anyway there are some ways to keep the munchkins happy & occupied on the plane, hope this helps, Marina