Invite local experts in various components of seed conservation to speak in the classroom. For example last year in Edmonton Sharon Rempel began speaking on the USC Canada's Seeds of Survival program, as well as the role Heritage Seed Program plays in thinking globally, acting locally. Then Dr. Robinson talked on heritage chickens. Simple, but very effective. Think about hospitality for your guests, the people visiting Seedy Saturday including your display people.
Food provided by a local catering service provides healthy food items for sale.
The refreshment area is a great place for folks to share information on growing plants, etc. Make sure you have an area near to the 'seeds to swap' table where folks can sit, talk about plants, etc and have a cup of tea. Advertising is important. Make up a pretty poster that you spread all over your region. Make a one page press announcement and send it out to every radio show, paper, etc.