Is there a way for you to find out the psycho/demographics of people attending the dog show? Do they track some sort of stats that they could share with you?
It's good to look professional, but it's better to tailor your branding to appeal to the people most likely to see it. For instance you may want to have two flyers/pamphlets - one that has images focusing on more pets being members of a younger family household, and another one that portrays pets as being companions to the elderly.
Also while at the show, I would imagine that there would be a number of other vendors selling specialty dog treats. What makes you unique? What will make people want to buy from you instead of someone else that's been doing it for years? Think of how you can differentiate yourself, be it through pricing, branding, or maybe even your own personal story.
Also bring samples =)