Sure, it's not as hard as the OP is making it out to be, but the OP makes a good point. 
  
There's no space, from the KS pledge levels, to add t-shirt size. 
  
Are they going to GUESS? 
  
Am I going to get a size small and have to give it to my son? 
  
I opened a support ticket, but this should have been a no-brainer.