Might I suggest getting a model that allows for input and output and not strictly for the Car. You’ll need a coupler but will be able to use these elsewhere and have the ability to have games systems or two different movies on them, but this will be a question as far as age ( since these will not have a headrest harness per say). You will need to look at good headphones or a RF modulator or mini cable or tape adapter (depending on the car).

If you gave just a little more detail i would feel better about a recommendation.