Gift Vouchers - advice please!

Hi all!
I have a number of customers who’ve recently asked us to start stocking gift vouchers so that they can purchase them for family and friends who comment on items they’ve previously brought from us. I decided to design and list some today to see how it goes and to redeem them I plan on having the customer put the item into their basket and contact me with the voucher code either by email or in the “note to seller” box so that I can redeem the vouchers and declare the item as paid for.

Has anyone had any experience of gift vouchers (positive or negative) and do you think that my method of redeeming them will work?

Thanks,
Dani x