At that age it might only be toddling around or being carried up and down the aisle- just to limit your expectations. The attention span isn’t massively there for all kids. Big bag of different toys, some that they haven’t seen before to keep whipping out…and lots of snacks.
i took my DD on a 4 hour flight solo at this age with the recommended sticker books and the post-its and the little suction toys. I had an iPad with headphones too but she had never used one before (and doesn’t have my phone) so she just chucked it down on the floor and wrapped the headphone wires around her neck 🤡 Toys went on the floor. She ended up playing with ice from the drinks trolley and being walked up and down the plane.
At 2 she is able to watch an episode of mr tumble on the plane and can do the sticker books. Your child might be absolutely fine to do this younger- but just a warning 🫣
I recommend a baby carrier so you can at least be hands free walking up and down the plane if it comes to that.
Re: restaurants I did two things in a holiday setting at that age.
If I wanted to have a nice dinner- I put her in her pyjamas, do bedtime routine before we go out, plan for a late dinner and then walk her to sleep first.
If I wanted her to be part of it- I would still put her in something cosy so she could be walked to sleep so we could have a quiet post dinner drink (as much as holiday frilly cute outfits are nice). I’d order her food immediately or take turns running around with her to time her eating with us. But I did not strap her into a high chair until it was ‘food time’.