I was there last month too. For the quick service places in Disney World I (Mid-twenties) was only asked for ID 3/7 purchases and two of those three accepted my Canadian driver's license. The third wanted a picture of my passport and I was denied as I didn't have one. So it is a good idea to have it but if you're doing the quick service or cart places they don't seem to care much.
At Universal I was asked for ID 1/3 times (Hog's Head checked) and they accepted my Canadian DL.