For vendors accepting creative kids voucher it is best to add a booking note in special registration instructions as follows:
CREATIVE KIDS voucher details can be added on the next page. Upon successful completion of the order where a Creative Kids voucher is filled out correctly, we will then process a refund to the same bank card that you completed the order with for $100. Please allow for 5-7 business day after receiving a refund confirmation email for the funds to appear in your bank account. Thanks in advance :)
It would then be advisable that you add 3 custom fields (See screenshot) to the bottom of the booking form
This would all be on a class level basis for the classes you're accepting the vouchers for.
If you want to, you could also make a note of this in class description that you're accepting vouchers on this class or add it in extra class info 8. Would you like to add an extra field to your listing profile?
You can sure this up further by including in terms and conditions and refund policy.