Has nothing to do with the DDP. If you're on the DDP and register with it when you book the restaurant reservations, you will leave a credit card guarantee for the normally prepaid restaurants - CRT and the three dinner shows. That's the only time DDP comes into play. If you don't have DDP at the time you book you will pay in full for these four reservations.
Whether you're on DDP or not, you will need to give a credit card guarantee for any reservation at Akershus, California Grill, Victoria & Alberts (which is not a DDP restaurant anyway), and special dining packages like Fantasmic Dining Package, Candlelight Processional Dining Package, or Lunch with an Imagineer (the last is not on the dining plan).