Little Feet
Simple answer ...... is Prep Prep Prep ........ either way with regards to the seating scenario will leave you with junior on your laps if the flight becomes full, so in my experience go for the middle seats and get little ones all comfy in the middle two, take it in turns with little on your lap and if there becomes a seat free near by, one of the grown ups goes and rests their feet leaving all little ones together.
Of course all the usual stuff should be taken care of - arrive early, bag full of small juice cartons, fruit, crayons, books ..... infact anything you can possibly carry without taking the kitchen sink ....
But most of all, just enjoy the experience and i'm sure the crew will help as much as they can ......
Enjoy your trip.
Tintop