I justed posted the below in response to someone who had the same question:
I struggled over this too as I am very frugal when it comes to eating out. (Share meals, order water, etc.). So, I sat down and priced out what our family of four would probably spend (DS 7 - child price and DS 10 - adult price). So I figured if I was paying OOP I would buy mainly CS except for a couple TS I considered a "splurge" because I really wanted to do them. For our family of four for 7 nights I figured OOP to be $885 and the plan was only $870. With the DDP we would get a lot more food including beverages and dessert (something I wouldn't do much OOP - I would have water bottles, etc.) Also, we would get to have 7 TS meals!!! This was a no brainer.
I suggest you take a look at the menus on allears.net and price out what you "think" you would order. This really helped me make the decision. (It ended up we got
free dining through my Disney Visa but this was well after I had booked and paid for the trip - we got a credit on our visa)
One last note - By choosing DDP I felt I would get to enjoy my vacation more because it would all be paid for and I wouldn't have to be pinching pennies and I could order what I really wanted like the $26.99 steak rather than the $18.99 chicken sandwich!
The only catch would be the ages of your kids. If you are doing character meals you will pay for them no matter what so the DDP would certainly be worth it. But if they are picky eaters and don't eat much and are planning CS meals - you might not want to and just let them share with you and pay OOP.