i doubt 2 LEDs will be enough to light an entire 10.4 panel. what you will probably have to do is build an array of lights to cover a larger portion of the screen.
then you can use frosted glass/plastic, or even fluorecent light fixture diffuser panels to give you a more even light source for the screen.
this might be fun project to investigate, but i would be willing to bet that the LEDs are going to be too weak to light the entire panel. i cant remember the terms for lighting, but there is basically brightness, and the strength of the light. think of it this way... if you look directly into a LED.... it is bright. but it really doesnt have much power when it comes to lighting up an area....
not trying to bash the idea, but give it a try. and let us know if it works... i would love to boost the brightness of my 8.4 lcd.