While Shire Silver cards are great for in-person transactions, sometimes you'll need to handle them over the Internet. We are now able to do this, although it isn't a totally automated setup yet. It should, however, be easily doable for your average web user.
On our checkout page, we have a checkbox for indicating that this purchase is a gift. Tell your users to check this box and enter something like "This is a donation to Rational Review News Digest" in the comment box, as shown below.
Optionally, you can have them enter your mailing address in the Delivery Information section. By doing that, we won't need to ask you where to ship the package. If we don't know who you are, we might have to ask your customer, and that could be awkward; so please let us know if you want to do this. An email via our contact page with your site name and mailing address should be fine.