Just go to the restaurant page through disney, it'll say if its two table service or not.
General rule of thumb is any Signature dining is 2, and some characters are 2 for lunch/dinner. I think all character breakfast are just 1 TS credit. Like akershus is 1 for breakfast, but 2 for dinner. Well except for CRT, i think its 2 all the time. 1 all the time example would be Garden Grill.
Pretty much any other table service is just 1 credit.
For an adult, eating a 1 credit character meal with an adult beverage is the highest value you can hit pretty much. Any other place, need to order most expensive thing they have on the menu and get an adult beverage. Will allow you to break even with the purchase price pretty much.
Kids, even when not free, you could save a little with them by eating 1 character meal a deal, the price covers that meal and then their snack and QS for the day were "free".
Since last year was the last time our oldest was a kid, we blew it out and ate a bunch of character meals that week. Once they hit 10 and you get flagged as an adult for them, the value goes to almost worthless, no way she eats $100/day in food, cheaper to just pay OOP as you go (with at a min 5% off gift card money, which you can also buy the DDP with incidentally). We still have two that would qualify for the free dining, but the 10 year old makes it not worth it still. If all 3 were still a kid, would probably do it.