The problem is that your children have no discipline, because you allow them to run around and do the business everywhere like wild dogs. You make him understand what exactly he is doing, and if he does it again, you make him do the cleaning. 3 year old or not. Just because he's a child doesn't mean there's no rule.
Well thank you Dr. Spock. Talking to him, and making him clean up, why did that never enter my mind? You have opened my eyes to a whole new world, I feel light as a feather.