Package Services to be loaded onto a physical card with a serial number. The clients like to leave with something physical to gift. The code on the card can be added or scanned just like a gift card. "Enter or scan package code" possibly under the gift card section at checkout, then those services can be loaded from the package entered to be bought. When the client presents the card or calls to book their services, it can be looked up to see the remaining services they have with the package they bought or were gifted. When the package service is checked out the code is entered to cover the specific service or services just like a gift card to remove that balance from the card.

I understand the vouchers do this on a clients profile but the card gives them something physical to leave with and it makes checkout more seamless instead of asking the information for the recipient getting the spa package so the vouchers are on their profile, especially if they do not have an existing client profile already.