I've flown alot with my little ones.
The longest flight was 12 hrs when they were 6 mo and 28 mo.
No need to medicate them.
Remember to bring plenty of nappies in your hand luggage in case flight is delay for 9 hrs...worst case scenario.
Bring a lunch box with various little treats to dole out...raisins...bread rolls...maybe jellie beans. Bring an empty sippy cup or bottle. and you can fill it once you get to the other side.
If she has a dodi bring it...that will be good for the ear popping.
I forget what stage they are at at 20 mo (my baby is 3 now)
But the mini magi-doodles are great...especially if they haven't seen them before the flight...and the portable dvds too.
Crayons and a few pages torn out of a colouring book.
Generally I find they are fascinated by the goings on are generally very well behaved...cept for the time my 2 1/2 yo was banging the tray off the seat in front and I didn't notice cos I was gas-baggin to the lady opposite..passenger had to tap me on the shoulder
Another thing I found brilliant at that age was the little back pack with the harness...gives them a little freedom and you can take your eye off them to look around
Up to recently they were available in The Great Outdoors in Catham St in Dublin City Centre