I know of an easier trick.. worked a treat and cheaper
I got an ipad with an Ipad mount. worked like a dream and i drove 1000 miles and my daughter never said a peep
Another way is to get a folding case for the ipad and then get an elestic velcro strap.. tie round base of headrest and then feed the cover of the ipad through the strap.
Dvd plays in cars are so restrictive, not HD and you have to keep changing disks.. Ipad, load it up with cartoons and kids games.. bingo!