I would say that you should think about where else you would want to eat. You know the cost of the HDDR, so just match up that money against what you would otherwise spend.
For example, if you pay OOP for the HDDR, pick the two restaurants you would use those credits at. Choose meals from the menus listed online, and add up the cost. If it's more than the HDDR, pay OOP. If it's less, use your credits!