I’m not a fan of the unpaid internship but I agree you absolutely must pay attention to the laws, and you should make any moral decision inline with a legal one. But I think the moral decision is to pay them in line with the law if they are contributing to your company. An intern who is helping with “execution” sounds like an employee you should be paying. And if they are truly helping you execute, and they are doing it for no pay, you better find a way to make them happy because you wont find a better future employee.
Beyond this, I am assuming you have all the proper legal documents in place for your business and employees and interns.