Great tip about putting the movies on the hard drive! It does seem to eat up batteries.

ITA about the headphones. Read that other thread. I don't recommend the "bud" style at this age.

For such a short flight, any DVD player should do. Some have a battery life as little as 1 1/2 hours so maybe one with 3 hours would make more sense (check the difference in price). You can put the screen on "night mode" to save battery life.

We do long haul flights so I had to get one with at least 5 hours but with the cheaper models, you can actually buy a second battery. In the car, you would plug it in so it's not an issue on long drives.

Be clear to him that using the speakerphones is NOT an option. Do what I did and don't even let him know that it can be done. For ages she thought that the sound only came through the headphones. There's something about the acoustics on an aircraft that makes these devices extremely annoying, even when played softly.