Yes it will. I just ordered my DDE card for our September trip even though we have the Dining Plan. I verified from a CM at Disney that I can use it for all extras that are not covered under the dining plan such as Alcoholic beverages, extra add-ons for the main course that aren't in the plan, etc. It can even use it if I want to pay OOP for one of our kids meals at a TS.
We plan on eating breakfasts at our resort and I can use the DDE card for those as well.
My parents are meeting us for dinner at Coral Reef and I can use the DDE card to get the discount off of their meal since they aren't on the meal plan.
I know I will be back next year as well, so the $50 investment will definitely pay off in the long run.