Hey Janet-
Having you stop by the Disney Parks Moms Panel makes me smile like Cheshire Cat. I am so glad you asked this question because many Guest want to know if they can visit Table Service restaurants for just dessert and drinks. The answer is yes, if you are paying outside a Disney Dining Plan.
In your situation you are making a 50's Prime Time Café Table Service reservation and want to use your Quick Service dining credit for a dessert or milkshake. While I love this plan it is in not within the scope of using a Quick Service meal or snack entitlement. In order to avoid paying out-of-pocket you would need to change your Disney Dining Plan to one with Table Service credits or choose a Quick Service restaurant like the star studded, ABC Commissary. I love the
hip, fresh dishes they serve.
Disney Dad Tip: If you are looking at the desserts and milkshakes served at the 50's Prime Time Café then I would suggest pulling up a stool at the
Tune-In Lounge connected to the 50’s Prime Time Cafe. You get the same ambiance you are seeking without having to tie yourself to a reservation. My suggestion: Put the pedal to the metal and get the PB&J shake. You’ll flip over it!
Janet, enjoy making and eating many Magical Memories!
~Jason ºOº