OP- ignore the people who are not helpful.
Things that worked with my 2 at that age.
Sticker books- especially the usbourne ones.
Snacks, snacks and more snacks. I took their lunch boxes filled with lots of little packets of things... chocolate buttons, mini cheddars, little cereal bar type things, hula hoops... Put a few treat things in too. That used to keep them busy.
Apps/games on a tablet and comfy headphones.
We used to have an app called Video Touch- vehicles.
It was lots of 30 second clips of things like fire engines, bin lorries, planes, boats, motorbikes etc. I think it cost a couple of quid from the App Store but it was worth its weight in gold. There were others for animals/ pets/sea life too.
A magazine with a load of free tat on the front. They didn't set eyes on this until we took off so it was a new novelty thing.
A few story books to read.
Triangular crayons (they don't roll away) and a colouring book.
Baby wipes and a nappy sack to use as a bin!
Honestly- it will be fine. These things are never as bad as you think. He's old enough to understand what's happening and he'll be so excited.