I can't answer about loading the gift card, but may have some insight into your tax deduction.  The best answer is to ask your CPA, but I can tell you how it works with us.  Because you aren't "technically" giving any form of monetary donation, there isn't anything to write off.  You are basically giving your goods and services which works itself into your tax return because you aren't taking a payment for said goods and services.  For example, say you purchase your goods to sell, don't take any money for those goods, but donate them instead.  You still spent the money, but it you get nothing back for it.  That number will come out of your gross income at the end of the year.  Generally, you will owe Uncle Sam a little less.