Hi, Holly! I may be missing something here, but if you're getting free dining, I'm not sure why you would want to downgrade. You see, you can certainly use table-service dining credits for quick-service meals, but with all the various table-service options throughout the WDW resort, I think you can find plenty of TS restaurants that can even suit squirmy guests. And believe me, I've had some of the squirmiest over the years!
So, keep what you have, and take a look at the various options for using your
Disney Dining Plan credits. I think the character buffets as well as some of the casual TS restaurants at the resorts and parks are going to be well-suited to your traveling party.
Come back if you have more questions or concerns or if you need specific recommendations. Have a wonderful day and a magical vacation!