We have the DDE card -- and for our next trip in June we plan to do the meal plan.
However -- we will be using our DDE card for any charges during our meals that are not included in the Dining plan -- ie: cocktails, desserts for the kids if they want to order off of the adult menu etc.
According to a reply to a recent post of mine, the CM gives you a separate check anyway for drinks, so the DDE card will be applied to that check.
Hope this helps.
That being said -- if you really, really want to eat at the restaurants that require 2 vouchers, I would go the DDE route (Jiko, Cal Grill, Yachtsman, Artist Point, etc.)
After we broke even on the card, it has saved us well over $200 on our last 3 trips.