Seconding (thirding?) Brynda’s recommendation of lots and lots of tiny surprises that you can spring on the kids as needed for distraction, entertainment and comfort. Snacks, little books, small toys, maybe even a loved toy that they don’t know will be along.
Wear the kids out with as much exercise as possible before boarding the plane. Create a defined space in the waiting area for running in small circles, doing jumping jacks, doing sit-ups, marching in place, somersaults, whatever their level of coordination allows. You can make it a game of Simon Says to keep them focused. For E, do whatever you can to help him burn off energy.
One of my favorite things to do with a little guy is to stand with my feet apart, bending over with my arms wrapped beneath the toddler’s armpits and around the front of the chest. Now it’s time to help him jump – just a little lift to make him jump higher than he can on his own. Slowly build until the kid is jumping really high. They use lots of muscles doing this and think it’s great fun. Check with the flight attendants to see if there’s a place where they’d be OK with doing this on the flight, or if it would be Ok for your sons to walk down the aisles of the plane.
Good luck. Hope you have a great visit.