You will need to make some coding changes to add the category. Whether you are wanting to add it to the Order notification going to customer or to the Sales-order view in the admin module you will need to code to add the category. You may be wondering why it's not there now within the order info. It's because, as you know you can add products to multiple categories, so categories have nothing to do with product uniqueness. Products and Categories are a Many to Many relationship. NopCommerce uses categories to allow you to choose where product pages are accessed and NOT to somehow concatenate category to a ProductId for uniqueness. To do this without coding, make your products unique by festival. Add a festival designator in front of the SKU, then you can give it a description also. But you could make them all have the same ManufacturerPartNumber or GTIN or whatever so you can still group for reports if need be.