I recently sold my FG Falcon XR6 that had head rest DVD players.
Would I get them again, no.
For the amount of use they get, they are not worth the money. To watch a full movie requires a drive of 1.5+ hours, which severely limits the opportunities to use the DVD player in the first instance. Add to that the fact that a child watching a 7 inch screen while in the back seat of a car is a recipe for motion sickness, just ask my daughter.
In my situation, I would have been much better off getting a tablet of some description because they are a lot more versatile.