Some great tips here!
When bringing little ones that might be afraid of the dark on some of the dark rides, I bought little led keychain flashlights. It wasn't bright enough to bother anyone else on the ride, and just enough to distract them and help them feel like they were in control.
Another odd thing to bring is the post it notes to put over the sensor of the flush-by-themselves toilets. My kids were always a bit nervous around those things...
Other than that, we brought those Fun Tainer thermoses for the kids. It was nice because it kept the water cold, they fit easily in the backpack and in the fridge, plus it was nice to have for the flight too.
OH - and the Dollar Store tends to have some Disney items. It seems I have much less of a struggle getting them to use tissues, hand wipes or even hand sanitizer if it has a character.