For your event you may want to ensure you have no postage applied to the products.
This can include donation items or any items that your participant will be picking up at the event.
To do this you will need to set the merchandise items to Nil postage under the Postage Tab when creating or editing a product.
Shop > Inventory Management > Product > Search product > Edit > Postage Tab > Select postage Nil Postage to 'Yes'
It will then look like this on the form
