Fireworks with fisheye should definitely be doable. However, it depends on how tall your tripod is. There are going to be pretty huge crowds there for the fireworks, and the HK disneyland is tiny. This means you have to either back up to get away from the main body of the crowd which may mean you have to use a longer lens, or you have to get your camera above the heads of the people in front of you.
Any lens can be good for fireworks, but I'm assuming you want to include the castle in the shots, so you'll need wide.
I wouldn't try shooting fireworks by handholding the camera. You can get good results for handheld, but compared to tripod shots, they will likely not be very nice.
If you haven't shot fireworks before, definitely do some reading beforehand, it'll save you a lot of fiddling around in the field and you can actually just concentrate on watching the fireworks while just pressing the shutter release on and off on your camera (get your framing right in the first couple of bursts so you don't have to fiddle with the camera at all afterwards, then just vary your exposure times from ~2-6 seconds by using bulb mode on the shutter release).