Hi there, Tony!
You're really going to love visiting the Walt Disney World Resort during Christmas time!
With the
Disney Dining Plan, you are allowed to use a Table Service credit for a Quick Service meal if you choose to. Most restaurants don't have a problem with this at all since the Table Service credit is worth more; however, I'd recommend trying out some of the fantastic
Signature Restaurants around property because you'll get a much better value for your money that way.
It was very nice that the Cast Member on your last trip gave you a voucher for a Snack. That is something that is not written in as a policy, but just a nice gesture to help you re-coop some of your cost. While I cannot say that they'll do that again, I will say that it never hurts to ask because you just never know. I wouldn't count on that for sure, but if they do it, you'll be pleasantly surprised!
I hope this helps, Tony!
Wishing you a Pixie Dusted vacation!
~Jackie