I think it's more important to know if you know/can distract your kids for that long.

My kid, except for the first one, doesn't do any of those things. Well, he'll get cranky if he's strapped in for over 3 hours. Actually starts around the 2nd hour.

However, we can distract him. We've never had a complaint cuz he's usually quiet. He definitely doesn't have an inside voice and likes to yell and hear the echo, but we can get him interested in something else so he stops yelling to see the reaction.

He's not super picky, but he won't eat everything. That just means we have to be well stocked with his favorites.

Does he follow simple instructions. No, he seems to have a speech delay. That just means we work harder keeping him occupied. He likes to run around, so we'll pass him back and forth between us. Or, he walks in our space in front of us. If we had to, I'd walk him up and down the aisles but luckily he hasn't needed that.

The point is, we were VERY prepared and did a lot of work during the flight to keep him from bothering others. Once, we sat in separate aisles when he was in kind of a kicking phase. That way, he kicked a seat one of us was occupied in. He did want to be passed over the seat which may have been slightly distracting to others, but he didn't kick anyone else's seat and he wasn't crying or screaming while doing so so the disturbance was minimal. We even bought a portable dvd player (and didn't buy the cheapest one) so that it had a long battery time to help distract him on one of our longer flights.

We also try and pick flight times where his usual nap falls sometime during that flight. If you've booked the flight already, hopefully it's during a time when they kind of wind down (if they wind down).