we have a spirtited traveller too. whereas my angel preschooler can sit and do stickers etc for hours on a plane Liv is active so what worked for us was letting her walk laps around the plane. everyone got to know her and she did this from 11 mo when she was just starting to walk and more recently at 20 mo old. she walks and we follow and she will stop and chatter /smile / nosy parker her way into everyone's business and i tell you everyone liked it - it does help that she is an adorable kid with curly hair that gets her attention everywhere - she is a little "ham" so it is like a show for other passengers. we stopped and looked out the back windows too.
other things that worked well - snacks, books, travel magna doodle, coloured pencils and paper, a sticker activity book to do with us, deck of cards (they make their own fun).
don't count on the sleep and just take it as a bonus if he sleeps on the flight. you know these spirited ones can push through if necessary as long as they have something to watch or do. if he does not sleep during the flight you can bet he will crash as soon as you get off
On our return from the cook islands in october liv only slept 1 hr over the course of travelling ALL day (from rising at 6am to leave until we landed in sydney 2 x 5 hr flights + 1 layover in New Zealand later...) and we got settled in a taxi to go home and she was asleep 2 min into that car ride
enjoy your holiday!!