There are many ways you can launch an online store nowadays. From Shopify, to WordPress plugins, to a full blown custom Magento store.
Gift vouchers are a complex product to sell online, compared to a dress, for example. This is because to make the process efficient, they require quite a bit of bespoke code. Gift vouchers need validity periods, which means they need to be calculated automatically at the time of order. They need unique reference numbers, to make sure they can’t be duplicated and redeemed more than once. You’ll need a system to search for and administer customer orders, including marking each voucher as redeemed as they enter your premises.
Whilst we’re sure your web designers are great, our experience tells us that when it comes to gift vouchers, it’s best to have a system which has been built for the specific purpose.