Im going on a long drive in my rx8 and was wondering how i can get the navigation dvd player to work while i drive so the kids in the back will have something to do

 

It's DVD-ROM, won't play movies. You'd need to buy a DVD player, plus something like this: http://www.avelectronic.com/NavigationVid-Switcher.html
It's a complicated install. Far simpler and cheaper to buy a standard portable player and forget about using the nav screen for showing movies - it's illegal while driving anyway.