Hi, April!
If you like to plan ahead with dining reservations, plan on enjoying character dining experiences, want to do one table service meal each day, and save some money, then the Disney Dining Plan might be a good idea for you. Character buffet dinners can sometimes run up to about $45 per adult (prices subject to change) so the Dining Plan can be a great value.
If you prefer to do a few quick meals here and there, and do not really want to take the time to plan for reservations, then you might want to pass on the plan. However, with 7 year olds, they might enjoy locations like Chef Mickey's, Crystal Palace, and Hollywood & Vine where you will dine with so many of your favorite Disney Pals. These buffets add up in price, so the Dining Plan makes it a bit easier on the budget. Each member of your travel party also gets a refillable beverage mug for your resort, so there is a bonus there, too!
I suggest to plan out your days, adding in where you will want to eat. If your itinerary includes that table service/buffet for each day, then I say add on the plan. If not, then no worries, just pay as you go!
If you need an outline of a dining schedule,
let me know your plans and I can give restaurant suggestions with approximate costs. This might help you with the big Dining Plan decision. Good luck!