travelitis,
That's a very good question. You can not use the Q & C vouchers for the character meals. For the most part, the Q & C's are for counter service (B& C being an exception).
There is a voucher option for a character meal lunch (but not dinner). For this, you would have to step up to the Vacation Kingdom Lunch voucher. These vouchers cost 29.50 each for an adult. (The vouchers include tax and 15% tip. )
Since Character Meals are per person, you would be overpaying about 10 per adult for a character lunch meal over what you would pay without a voucher.
The Vacation Kingdom Lunch voucher lists the following character dining options: The Cystal Palace (which is closed for refurbishment) and The Garden Grill restaurant at the Land at EPCOT. The price for an adult for lunch is 16.95 (Plus tax and 15% tip=19.94). Tony's (adult= 16.99 plus tax and tip). Chef Mickey's is also listed on the lunch voucher, but the voucher can only be used during the hours lunch is served and I don't see where CM's has a lunch meal. (It would not be a good deal, anyway).
Now for the question of Liberty Tree Tavern, Sci-Fi, 50's Prime Time--you can use the Vacation Kingdom Lunch vouchers for these. You can share a meal in this scenario. You can order 1 appetizer, 1 entree, 1 non-alcholic drink, and 1 dessert. In some cases, it might make sense to use the VKL voucher. I plan to use my VKLs for the Concourse Steak House at the Contemporary, Alfredos at EPCOT and possibly Le Cellier and I am planning to share with DH. (My goal is to at least break even.

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Good luck to you in your planning.
-DC