Hi Erin!
One of my children has sensory issues so I completely understand and Walt Disney World can be a sensory overload for anyone. My two top fun choices for Downtown Disney would be Rainforest Cafe and TREX, but the Thunderstorms and Meteor Showers can become a major issues very quickly. I recommend visiting the gift shops in these restaurants to get a feel of the atmosphere, my daughter was fine with Rainforest Cafe, but did not care for TREX.
My children really enjoyed dining at
Fulton's Crab House, although the interior does not scream fun for children, the thrill of eating on a "boat" made up for the lack of kid approved atmosphere. Another good option for a full service restaurant is Planet Hollywood, the atmosphere is lots of fun without being too overwhelming.
Perhaps instead of dining at a full service restaurant, try one of the quick service locations such as Earl of Sandwich or Wolfgang Puck Express, both offer delicious food in an atmosphere that is not so overwhelming. After visiting either of those locations, I suggest taking a stroll over to
Ghirardelli Soda Fountain and Chocolate Shop. The sundaes here are wonderful and is certainly pleasing to any child's or adults palate. I hope this helps and please let me know if you have anymore questions!
Enjoy your Disney Time!
Mandy