Depends on your eating habits.
Some people say the dining option on MYW is too much food, and too restrictive (snacks are only ice cream bar, popcorn, etc). Others say it's just fine, and they couldn't live without breakfast. Some say the "good" restaurants take two credits (vouchers? tickets?) and others say that they wouldn't want to go there anyway so it doesn't matter to them.
DDE is 20% off, flat rate, every time, but you still have to pay for the tip. Costs $50 (or $75, depending on how you're getting it.)
Ok, so the MYW thing is $35 per adult, $10 per child per day. That's one sit down, one counter service and one snack daily (you can use them all on one day if you wanted, but who would want to?)
Figure out how much you think you'll eat and whether you want to be restricted to certain restaurants/snack carts and you'll have your answer
