For categorisation of discounts, it is best to consult with an accounting professional. You can find QuickBooks Online Certified accountants and bookkeepers in your area by clicking on the link below:
I would suggest adding the DIne and Discover vouchers as discounts on sales receipts, but please check with your accountant to make sure that is the best practice. For more information on adding a discount to invoice or sales receipt, please see the link below: