We have t
his Zenith brand one. This is our second portable dvd player. The first one (initial brand bought at
Walmart) only had a 4" screen and was getting old and starting to not work right all the time, so we upgraded to the Zenith.
What I love about our new player? It has a swivel screen so you can flip it around so all the buttons are on the back. When our ds was your younger childs age, he loved to push the buttons, which could be very annoying (especially for you older child! if they are watching it together). I so wish we had a player like this when ds was younger.

Also, this player has dual headphone ports. We also bought
these GE flexible kid headphones for ds. They are sized right for a kids head, and are flexible so that kids won't break them easily. We bought them at Target. Your kids will either need to wear headphones, or listen w/out sound on the plane, otherwise, it will really annoy other passengers.
eta: also, the battery life seems decent on the Zenith model. It lasts at least 3 hrs.
hth!