Hi Erin,
I've done something like this before. Not a whole lot you need to know. Many vendors like Starbucks are good about managing corporate e-gifts these days. There's no reason to make it any more complicated than it should be, so you can just download your registrant list right before the event, once every week, or as often as you'd want. Then go to your vendor's e-gift site (like Starbucks'
here), write your message, add your logo, choose your amount, upload your recipients, and fire away.