Hey Kathy!
I'm not sure how having a coupon will help with you giving back to breast cancer research? Usually when i hear coupon, your taking money off for your customer, not giving money to an organization.
Have you reached out to bloggers? I know that breast cancer research is popular, so maybe if you find a blogger to do a write up about you and that you are running this fundraiser.
Also, have you promoted on social media anywhere?
Also put a little thing about you giving back in each of your items. Many times if a person is on a mobile device or going straight to an item, they won't see your announcement.