Flying Internationally with Children with ADHD and ODD

So me and my husband and his family are taking a 2 week vacation with our 3 children to England. (Exciting and super stressful) Our son has been Diagnosed with ADHD and ODD and the most he has ever done is gone camping or a 10 hour drive to see family. Nothing quite as huge as this trip.

When we fly out we will have a 7yr 5 yr and 3yr old. I know that we are taking a night flight to avoid busy kids on the plane but I am terrified for everything. I know that I overthinking everything but what can I do to make this trip easier for him so there isn't a lot of things that over stimulate his little brain and cause a complete meltdown while on this trip? Its hard on him and people now days are cruel and will just see it as he's being a naughty kid and he sees that and it his feelings get hurt even more and there is another melt down due to that.

Any of you do Long haul trips with children with this different situations? How should I prepare him for something like this?

Flying Internationally with Children with ADHD and ODD
Danielle HernandezSalt Lake City, Utah
About Danielle Hernandez
Current: Salt Lake City, Utah
Birth: November 23
On since: Mar 9, 2017