On some models the LCD screen turns off when using video output. My gut feeling is not, but in this regard, you would have to test each as 'players' to see if one or the other (or both) keeps the LCD screens active when sending video out to the other player. And just a suggestion- if you need help on which particular cables to use, please post the exact model numbers, as they're all a little different ;).
I have two separate portable DVD players for my car (sony and LG) and both players have AV in and out ports. Is it possible to connect the two players together so my kids can watch the same movie? If so can someone enlighten me on the correct wires to use? Thanks