Any experience in planning for a large group?

[Esther]

I need any experienced folks that have done planning for a large group that includes food. I have no idea how many people will actually show up.

Any suggestions on how to determine how much food to prepare?

Foods:

gumbo
Pickles
corn dogs
nacho's
sausage on a stick
onion blossoms
cotton candy
pop corn
snow cones
desserts
drinks

I don't want to run out of food, nor do I want to invest unwisely.

This will be a fun day for kids and adults open to the public.