I'm building a website in Drupal 7 that offers local delivery for baked goods and such. There is no store front, no shipping and transactions and delivery dates need to be handled online.

Instead of the shipping tab step during checkout process, would it be possible to hook into Drupal's form API or the Drupal Commerce module to alter this "Shipping" page (see attached example). I would like the page to say Delivery instead of Shipping and allow the user to select an available date/time during certain work hours. This could even be as simple as a text field. There would also be a flat delivery fee.

If this is not possible, what are the alternatives? A paypal button on the item details page? Some other Drupal module?

Thanks for any suggestions.