Punish the people in addition to the business. Anyone who knew, or would have any reason to know, the age of the child should be fined if they are given prohibited duties and jailed if any harm comes to the child while tasked with prohibited duties.

Nothing will happen if a business is put out of business, rich people will just scoop up the resources and continue on with a small cost of doing business. All corporate and business practices that harm people (employees or the public) need to have the chance of jail time for business leadership to discourage it in the future. It doesn't even need to be draconian, just consistently enforced at the individual level.