There are other ways young children can stretch their wings. In the grocery store, you could send him to the end of the aisle to get a loaf of bread. You could leave him in the house for a few minutes while you go next door to pick up something from the grandparents. As you see how he does with these little steps, you may have a better sense of his readiness for a bigger step. Think about your son's development and personality.
Some children pay a lot of attention to details and to safety.
Others can get very absorbed in a particular activity and forget about everything else that is going on. A child's forgetfulness when an adult is present could just merit a reminder, however, if a child were home alone, it could create a safety issue. Emotionally, some children feel very comfortable being alone. Others prefer not to be alone, or are quite fearful at the prospect. You will receive clues from your son about his readiness both by what he says and how he acts.