Hi John,
In the cases screen only the contact you select will get the case notification, but this is something that can be changed. Take a look at how sending an email from the invoice screen works, it sends it to all the contacts that are not opted out of billing.
Another option that may work that would involve no customization (I haven't tested this but I think it would work) is to create a contact that has everyones email address in the email field seperated by a ';' and then select that contact when you want to email multiple contacts for that customer.
-Michael