You're fine.
Cookies are no big deal. I've listed cookies on the customs declaration form and have never had a problem.
a. fruits, plants, food, or insects?
b. meats, animals, or animal/wildlife products?
c. disease agents, cell cultures, or snails?
d. soil or have you visited a farm/ranch/pasture outside the United States?
Here's the duplex customs declaration form:
Below is a link giving you further explanation to each part of the form.
http://www.cbp.gov/xp/cgov/travel/va...ation_form.xml
As you can see, you will itemize each purchase on the back of the card and list what you paid for it. Whether you carry them with you or pack them with the luggage you check in is up to you.