Regarding the FairPlay voucher, another client customized their registration form as follows:
(Schreenshot #1 - Online Registration Form)
(Schreenshot #2 - Invoice)
If people want to use the FairPlay voucher, they have to enter the voucher number or TBA. If not, they can't submit the form.
Let us know If your club also want to apply this customisation to your online registration form.