Scoring Statistics - Double or Single on Error

Question
I am the score keeper for our 5th grade recreational softball team.  I am putting together some stats for the coach and I don't know how to score a batter who hit the ball, reached first where the first baseman missed the throw and the batter/runner advanced to second base.  Do I score it a single or a double for the batter's stats?

Answer
There are two ways to score this.  To determine which way to score this, one question needs to be answered.  Would the batter have been out if the first baseman had not missed the ball.  If the batter would have been safe at first regardless, you score this as a single.  The batter advanced to second on the error.

If the batter would have been put out with a made play at first, you score this as an error, there is no hit.  In the score book, instead of marking the hit you record an E3, indicating the reason the batter made it safely was because of an error at first base.  In this case, this counts as an at bat with no hit, thus hurting that players batting average.  One more thing you only score an error on the 1st baseman if the throw was catchable.  If it wasn't you score the error on the player who made the throw.