Dining Plans are NOT meant to save money. They are a convenience of pre-paying and not having to count pennies at the table. Each and every time that receipt printed out with the OOP costs, we sighed with relief and scanned our Magic Bands.

But we are a party of three and our DD is a massive sushi fan. OOP paying at Tokyo Dining dinner would have been an easy $160! Garden Grill? Another $130. The stress this would have caused us every four hours at mealtime, well, we were happy to overpay for the Dining Plan.
Saving money is going to come into play with your
Hotel (on or off-site, kitchenette or not), your
Tickets (Hopper or No Hopper? Water Parks? 4 day versus 10 day),
Souvenirs, and
Other Purchases (first aid, sunglasses replacement, etc.)
[Edit: I just realized this could be a great acronym!
THOSE things!

The E is for Etc. ]
However... some people "save money" because they eat at the more expensive restaurants and if you spread that cost across your party, it can seem like you've "saved money". As pointed out, the kids usually eat very little at Character Meals because they are easily distracted by a giant stuffed animal walking around.
Meals at WDW are just plain expensive, no matter which way you work it. I would suggest possibly ordering non-perishable food online for hotel delivery, splitting up the meals between your whole family (most portion sizes they slap on a plate are MORE than substantial for two people!!!) and bringing water bottles as they do have water fountains everywhere.
And remember... it's Disney so you actually have two kids and four adults when it comes to the food.

The older ones aren't supposed to order off the kids menu, the younger ones aren't supposed to order off the adult menu. If you get a server who doesn't mind, they may ignore this, but the policy is the policy is the manager's discretion.

I know for our small family, once we got enough dishes on the table, nobody minded when we asked for extra plates and we all shared bites of everyone else's meal. So maybe it won't even be an issue for your family...
YMMV but depending on how many times you have gone before, if you haven't experienced all the Character Meals, I'd say it has a higher value than say, before you've done 6 of the Character Meals. If you're not interested in repeating them, then the value kind of drops off... My family has done a small sliver of them so I am planning our next trip with Dining Plan to incorporate as many Character Meals as we can comfortably manage on a vacation that we still walk miles each day on....