Balk - Babe Ruth League - Has ANYBODY ever seen this happen before?

[KCScharlatt]

This instance happened last season, but I have never seen this happen before. Babe Ruth game. 2 man crew, I'm the base umpire. Bottom of the 7th. Winning run on 2nd base. Additional runner on 1st base. Runner on 2nd attempts steal when pitcher hasn't started his motion. Pitcher then starts his delivery of the pitch to home plate, and then stops his motion. When he stops his motion, the runner was ALREADY standing on 3rd base. I called time, and issued the balk. Now, because the runner had successfully occupied the next base by the time of the infraction, the balk sent him home to score the winning run. I know this is an off the wall play. But out of curiosity did I make the right call by sending the kid home to score the run?