No, there is no cause of action. The standard for determining whether someone has acted wrongfully (and therefore could be liable) is almost always the "reasonable man" standard: that is, whether an action was negligent, careless, etc. is judged by the standard of the average reasonable person. It is not judged by the standard of the most vulnerable members of society--e.g. young children or those with mental disabilities--unless and only to the degree the action is aimed squarely at them. The television ad you describe is aimed at adults, and it will not cause harm to the average adult, or likely even the average non-impaired child old enough to watch the sort of stations and programs which would air this ad. The fact that your brother, as a particularly vulnerable person, was susceptible to the ad does not mean that the restaurant or marketing company did anything wrong.