Hi Kathy,
Anyone is welcome to order off the children's menu, even if the guest is on the Disney Dining Plans. However, if any of the guests are under the age of 3, they aren't part of the paid dining plans. Therefore, you would need to pay for that meal out of pocket.
Also, adults are able to order kids' meals, too. My mother is a light eater; and when we visited Walt Disney World with her, she ordered off the children's menu many times without any problems.
By the way, Walt Disney World is introducing some
new kids' menu items at the Magic Kingdom that look tasty!
Thank you for the question; please let us know if we can help again.