If you can use those credits elsewhere you may be better off paying OOP for CRT Lunch. The approximate 'value' per credit at CRT is $17.99 for an adult, as the price for lunch is $35.99.
If you're going during one of the holiday increases, your value per credit increases to $19.99.
Here's how your day would break down cost wise
$69.99 - Adult DxDDP Cost
-$35.99 - CRT Lunch Cost
-$2.34 - Value of Tax (you'd pay tax OOP, no tax is added for using DDP or DxDDP Credits)
$31.66 - Left over to use for Dinner.
To come out ahead or even on the day, you'd want to choose a more expensive TS restaurant for dinner that night.
As I said - if you can use those two credits elsewhere for other lunches to balance signature dinners, you may be better off doing it that way.