Hey @chris - good question! I think there are multiple ways you could tackle this (and I'm betting other folks here in the community will have ideas on top of mine).  But here are my thoughts:

1.  You could send the $25 gift card out to customers at a later time. That way you wouldn't have to keep track and handle it during transactions during the busy shopping days. At the end of the day, you could just pull a Report to tell you who spent over $125 and should be sent a gift card. (Either physical gift card that can be picked up in store or eGift card that could be emailed to them). If it was me, I'd do it this way and just email them the eGift card after the fact. This way, you also have a reason to collect new customers' email addresses for future marketing.

2.  You could do exactly what you outlined above - $25 gift card to the sale, then add a $25 discount, however, I don't know that there's a way to hide that on the receipt. Maybe it's actually nice that it shows the customer that they got $25 FREE?