Hi Amiee!
Thank you for visiting the Moms Panel!
I understand your wish to choose a more healthy option for dessert. There are many restaurants at Walt Disney World that offer a "no sugar added" dessert choice (including Grand Floridian Cafe, Artist Point, Le Cellier, The Wave, Tony's Town Square, Kona Cafe), and there are several that offer fresh fruit as an adult choice (such as Hollywood & Vine, Whispering Canyon Cafe, Chef Mickey's).
A good website that I always refer to is allears.net, which has a full menu listing of most restaurants at Walt Disney World Resort - this may help you decide which menus will suit you.
An adult is generally not permitted to order from the children's menu, but please do not hesitate to ask your Cast Members for alternative healthy options. Chefs and servers are happy to work with their Guests to accommodate everyone's tastes and dietary preferences.
If you have any other questions, please come back and ask me - I would be happy to help you plan your magical vacation!