I know this is a circus theme, but is it a 'formal' banquet? What I mean, is it an event that is using some circus thematics (like balloons and popcorn on the tables) or are you going for circus fare?
Here's what I was thinking...
> Little, battered corn
dogs as butlered appetizers with a maple dipping sauce
> Individual pizzas
> "Adult" Snow Cones - shaved ice with liquors (like Midori,
Chambord, etc) as the coloring
> Smoked turkey
drumsticks
> Caramel corn, made on site
> Warm Cashew brittle
> Stuffed funnel cakes, with cinnamon apples and whipped cream
> 'Slider' hamburgers... 2 oz patties on little square rolls
> Hand cut french fries
Hope this helps.