Last year, we traveled with our 2 sons on an 15 hr. directly flight. Plus there was a 6-hour delay before we took off. At that time, our first son was 4 and the 2nd was 1.5 yrs. old. I bought small toys from the dollar store, such as cars, stickers, books. We didn't really bring our "good" toys from home because if they lose these toys, it was no big deal. I wrapped each set of toys with tissue paper and I would whip each one out periodically if they got bored. Part of the fun was them unwrapping them!
I think most flights have little screens for each person to view on now so I found that really help. We also brought a few organic lollipops for them to suck on for take-off and landing so their ears won't pop. Definitely brought lots of snacks for them too! Hope that helps! Have fun and enjoy your trip!