K.L.
Picky eaters are so stressful, eh? My four year old was like that for sooo long. She would only eat four things too.....I'm sure your pediatrician will agree that as long as they are in the proper percentile then you shouldn't worry.
I on the other hand would get sick of making 2 seperate dinners every night, lol.
But then as soon as my daughter turned 4 it was like a switch went on.....she could do anything and eat anything because she is big now and she is 4, roflol....
I have read that a child has to be introduced to a food for at least 80 times before they know if they like it or not.
I would suggest putting one spoonful of food on the plate if he eats it then great....if not....not much is wasted.....good luck....K.