If you are planning on using all of your Table Service meals for Counter Service you'd probably be better off without the DDP. You will spend much less just paying OOP for your meals.
2 Adults on the plan $37.99/night
2 Children on the plan $9.99/night
Take a 7 Night/8 Day Vacation
Adult DDP Cost $531.86
Child DDP Cost $139.86
Total DDP Cost $617.72
Average Adult CS Meal with Dessert $13.00
Average Child CS Meal Cost $4.49
just a head's up in case you didn't realize... you do not have to use your Table Service meals only at dinner time... you can use them for breakfasts, buffets, character meals, lunches, etc... it's very flexible...
when my kids were younger we almost never ate sit-down dinner, but almost always ate sit-down breakfast since they enjoyed breakfast foods much more
According to the DDP information on Disney's website, no, you can't use Table Service credits for Counter Service meals. This MAY be able to be overridden by a location manager, but you should not count on it.
I'm wondering why one would want to use the dining plan if one was mostly interested in eating counter service. The value of the dining plan comes mostly with use of the table service credits.