Hi Donna,This happens with small kids often.With time he will improve!Esp with other kids in play school!!!
Meanwhile give what he wants and likes.
Always keep trying new things,new taste,new flaours etc.One thing or other will click! Do some garnishing for food to make it look attractive!!!
Definitely he needs some multivitamin
and multi mineral supplement.Give him once a day whatever brand you can get over there.