imported post
That sucks.
You mentioned that several other parents had approached you and expressed their appreciation for your carry. Perhaps you could approach them and ask them to express their opinion to the coach? Both of your carry and her response. And the coach's response, for that matter.
Or if you wanted to stoop to her level, you could find out what PD her husband works for and file a complaint, saying that she was using her husband's position to intimidate people into trampling your rights under color of law. She certainly used it with you, so I'm sure she used it with the coach as well. It wouldn't actually carry any weight, but it would embarrass him and might get him to ask her to back off.
That second approach is very distasteful, but it occurs to me that it's not unlikely that this is a pattern of behavior with her, and you might be doing everyone around her a favor by getting her husband to rein her in.
Assuming you don't want your kid off the team, the other thing you should probably do for a while is wear a cover garment. Bonus points if it absolutely covers the firearm, but yet makes it completely obvious that you're carrying <evil grin>.