Completely disregard the corn...that is normal for MANY people. It has a very hard outer coat that is nearly impossible for the human digestive system to break down.
All the other things you are listing are quite non-digestible food...especially a two year old that isn't chewing so well. I noticed around two that I really needed to start teaching my toddler better chewing habits...she was swallowing the most weird things whole.
If he is otherwise growing, active, and hitting his milestones you probably don't have much to worry about. A well-balanced and healthy diet will keep him in good shape.
The human digestive system is not incredibly efficient at breaking down many foods, but it is quite good at extracting the nutrition a growing body needs. I would be more concerned about your daughter's infrequent, hard poop rather than regular, healthy bowel movements.