My kids go to bed pretty early, and the days we try to keep them up late (Wishes, Fantasmic!), they are begging to go to bed, so we keep our late nights at a minimum. Plus, they wake up early no matter what time they go to sleep. Grumpy kids makes for a miserable day! They also don't care for WS at Epcot, so we try to time that with when they might take a nap and rush through as many countries as we can while they sleep in the stroller. Even with the nap, we haven't made it to Illuminations yet.
Really, you know your kids and what they can handle. And, while it isn't necessary to plan everything around what they like, you probably do want to keep them pretty happy and well-rested for your own sanity!