There is definitely a required dress code when spending the day at a thoroughbred race track, although it varies based on where within the park that the event will be hosted. And it is helpful to confirm attire requirements with the parks group sales or special events contact.
As a general rule, it is helpful to notify guests that business casual is the minimum requirement. This means no jeans or sneakers.
However, the park will require a more strict dress code if the event is hosted in one of the more elegant banquet/dining rooms or track suites. In such areas of the park, it will not be unusual to require guests to wear jackets, blazers, shirts with collars, sweaters, dresses, pantsuits, dress shoes, etc.
In addition, shorts would be considered inappropriate in such areas.

