The only discount card is TIW. You need to be a Fl resident or AP holder. I do not know what Fl residents pay for TIW, but the AP rate (which is cheaper) is $75. The break even on that is about $375. I do not think you would spend that at Ohana and Whispering Canyon. The TIW is only accepted at TS meals with the exception of the QS at certain resorts, POP being one of them. You need to decide how much you would spend during the week to see if it would be worth it. Again, you would have to be either a Fl resident or AP holder. There are restaurants that offer an AP discount which is 10% off (rather than the TIW 20%). We have used an AP discount at Whispering Canyon, Chefs de France, T-Rex, to name a few.
In our case I feel it is worth it in my opinion to be an AP, but we traveled to WDW twice in the past 12 months. We ate at a few sit downs each trip(though not once a day) and paid OOP for food. We spent about $600 on
QS and TS, 1A and 1 10 year old and we shared some. We spent about half of that on TS and about half on QS (and used our AP discount a few times).
If you want to eat at any TS during your trip, you will need to plan to a certain degree. You should have an ADR for each of your sit down meals, at least.