We took our just 2 year old on a long trip a couple of years ago that involved several flights at all times of day. I was absolutely dreading it but it actually wasn't too bad
!
As previous posters have said, don't rely on aeroplane food, none of my kids have ever liked it, snacks are the only way forward. Love the sleeping bag idea, definitely nicking that one! If you can fit it one of your pillows is a good idea, smells of home and makes the seat a lot more cosy/comfy. I'm afraid we were also pretty dependent on the iPad, best apps we had were Peppa's Party, Lunchbox, 123 ColourHD, but we also downloaded some of his favourite TV programmes. Might be an idea to get some kids headphones too, the plane ones are too big and just slip off which is frustrating and definitely led to the odd tantrum.
Lastly, almost everyone on the plane will have been in your position at some point, so if your LO does have a meltdown don't worry. I remember the end of our final flight of the trip when, having turned 2, he had to sit in his own seat. Queue the mother of all tantrums! All I remember is having to hold him in his seat, him screaming that he wanted to sit with me, me in floods of tears. I looked up and locked eyes with a woman on the other side of the aisle from us, she smiled at me and mouthed "just breathe, you are so nearly there!". Needless to say, as soon as we landed he fell fast asleep!
Have a fabulous trip wherever you're going!