If you log into your own account, you will find a section in My Portfolio called Gift Certificates. If you click on that link, you will see all the GCs you've bought, and information on when/by whom they were redeemed (if they've been redeemed). That table will also show you the Amount each is for, and most importantly the CODE you need to redeem them. You can write down the code, sign out of your account and into your friends, and have them use that code along with your email to redeem the certificates into their account for Kiva Credit.
It works!

(And yes, if you want to print the certificate later from home, rather than have them use the codes now, you may do that!)
Hope this helps,
--Diane.