We have in house industrial laundering service to support our distressed applique biz. Its available for post laundering discharge but the additional expense is usually cost prohibitive. For our Resort line it is never been an issue as the typical end user will not wear the shirt until they return home and launder the garment(s). As is the case with most end users in general. That said I produced a huge order for a major tennis shoe co for a Boston Marathon event. I was a bit concerned that they would pass these out and wear them during the event. Perspiration combined with an unlaundered discharge garment is often prone to reactivating a sulphuour odor and, in some cases, can cause a rash. I advised them accordingly.
In the end I would never advise anyone not to post launder or stamp a "Wash before Wearing" sticker on a garment; it's just that we have rarely found it necessary. Lastly and perhaps most importantly I would be far more attentive to the issue when decorating childrens apparel.