You should be fine.

I took my son back to china when he was 2, 3 and 1 year old. Just he and I.
It's not bad. Just prepare some toys he likes, such as Legos, color sheet, puzzles and books, of course his favior snack also.
I also took portable DVD player and his DVDs. Airline has disney movie available.
Let him watch half hour then rest do other play, then maybe another half hour.
I also took him walk on the plan, from front to end twice. Your kid might sleep several hours if you are lucky then time will seem shorter for you.