It has been years since I have done either. Pros and Cons?
We have table reservations every night and we will be there for 9 nights. Thought?
Judging by your signature, TiW.
In my opinion, there are two separate questions. First, does the dining plan save you any money? Unless you have kids aged 3 to 9, you'll lose money on the plan 98% of the time. Therefore, paying out of pocket is a better choice than the dining plan.
The second question is, will you spend at least $500 on applicable dining? If you have five people for 9 nights, with a table service meal each night, then it seems exceedingly likely that you'll spend more than $500. That's the break-even point for TiW. If you qualify for some other discounts, like DVC, AP, or Disney Visa, then your break even might be a little higher, but typically not by much. Those discounts are lower, not accepted at as many places, and don't cover alcohol.
So, I'd go with TiW for your family.