Sample site
Here, your gift card page opens.
On your own site, this link goes to the gift-card page your booking app or card reader already hosts. People choose an amount or a package, pay there, and the card arrives by email, ready to print or forward.
The payment happens on that page, not on your website, so the site never handles a card number. The Gift cards link sits in the menu on every page, so people find it without asking.
The terms on your site ("Gift cards never expire and carry no fees.") go up only once your gift-card settings say the same thing, so the site and the checkout never disagree.