I'm no pro but I think you should be fine.
Definitely have a tripod for fireworks and if you want shots of just the castle at night. Also either use a remote shutter release ($5 on Ebay) or the camera's built in timer.
Food, parades, characters shouldn't be a problem as long as there's enough light.
Biggest issue would be Spectromagic. Take some shots at night for practice (before you go on vacation) and play with the ISO. Go as high as you can without causing so much noise that the picture isn't usable. The higher the ISO the faster the shutter speed. The faster the shutter, the lesser the camera shake.