Have not heard of any substitutions, but the following are options for using TS credits:
The Plaza Restaurant, Beaches & Cream, ESPN are TS places that do not take ADRs. So if you are willing to walk up and wait you can still use your TS credits. There may be more like these.
Have you tried to book 2TS meals at places like Narcoossee's, Jiko, Flying Fish etc.? That is a one shot deal to use up those 2 credits.
Try for breakfast meals and also consider some of the resort TS locations (especially the moderates).
Finally, I've read there is a pizza delivery combo available for 2 adult TS credits (Pizza, salads, dessert and drinks).
Good luck with your dining experiences.