Hi, Karinda! This is a question best answered by your family, but I can give you my pros and cons based on my family's habits.
I think the dining plan is an awesome way to keep an eye on your vacation budget. Once you have the food budget pretty well set by the dining plan, you have most of the pieces of your vacation budget in place. By then, you will know the cost to travel, as well as the cost for your room and theme park passes. This is a great way for you to plan financially for your trip - and to see how much souvenir money you have left over! It also forces you to make some plans for when and where you want to eat. I have seen quite a few disappointed faces on my own family members who went down to Disney World with the intention of just "winging it", and didn't end up having the character meals they wanted or the dining experiences they hoped for.
On the other hand, I like having the option to order meals off of an adult menu for my girls, especially the nine year old, who isn't quite satisfied with a child's portion. My 19 year old daughter would never eat the amount of food included with the dining plan. That could be an excellent reason to have the dining plan - you might have a family of healthy eaters that appreciate having a very generous food allowance.
The dining plan is an excellent option for families, for the purposes of budgeting, planning, and for the amount of food you get for the price you pay. But this is something you'll have to weigh the value of based on your family's dining habits.
Have a great vacation!