I've eaten gluten free for two WDW trips, and had some really great food! Please note, I don't have celiac disease, but a gluten intolerance.
The DisAbilities area here at DIS has some great information. Also, contact Disney Special Diets and ask for their food list for CS locations (although I hear that list is a work-in-progress and is probably NOT current). When you go to any CS location, they should be able to let you look at the huge binder they maintain with the ingredients for all the items they have, so you can determine yourself if the GF buns will work for you, or if there are any ingredients that may not be completely GF.
When making ADRs for TS restaurant, mention that you are GF, and usually the chef will come out and speak with you before ordering to let you know which items are GF, or can be made GF. For example, I had some awesome GF fried chicken at 50's PTC, GF Mickey waffles at Tusker House, amazing GF chicken wings at Ohana, and a pretty darn good burger at Cosmic Rays with a GF bun and french fries from a dedicated fryer. Sorry, I haven't been to either of the water parks.
