Controlling font size for iOS application

I'm having difficulty programming my game to use different fonts while running on the iPhone, iPad etc. Basically I need to use different sized fonts for different devices, for example the text font for the New iPad would be larger than the text on the 1st and 2nd gen iPads.

This is a simplified version of what I was thinking (will be testing later today):

 var smallFont : Font;
 var largeFont : Font;
 
     function Update(){
         if(iPhone.generation == iPhoneGeneration.iPad1Gen){
             guiText.font = smallFont;
         }
         if(iPhone.generation == iPhoneGeneration.iPad3Gen){
             guiText.font = largeFont;
         }
     }