I've got an S3, but it's similar enough that settings should work out.
I haven't actually photographed Spectromagic (or anything at Disney, yet) since getting my new S3, but I have been practicing my low-light shots. Unfortunately, low-light is tough for a P&S, even a good one like the S2/S3.
You're on the right track with going manual ... you want to take control over the settings to prevent the camera from simply boosting the ISO to it's highest point (which causes lots of noise).
I'm not entirely sure, yet, but because some things are bright and some things are dark in Spectromagic, switching to Center-weighted light metering might help (maybe even Spot). You probably don't need to mess with the White Balance as most of the color is coming directly *from* the lights.
Setting the biggest aperture (lowest number) is one thing ... the bigger the aperture, the more light and the faster the shutter speed can be. You might be able to get a nice "star" effect, though, if you close the aperture to it's smallest (8.0) -- I haven't tried this, yet, and I've been focusing more on getting the most light into the camera.
I'd try keeping the ISO at 200 or less, but you might have to go to 400. If so, you'll need NeatImage/NoiseNinja/Noiseware noise reduction software ... there's just no way around it. A noisy image is still better than no image (usually) ... with the software, you'd be surprised what it can do!
After you've got the aperture and ISO set, try setting the highest shutter speed you can. Keep testing with the half-press to see what the camera thinks of your exposure. There should be a little number displayed in one of the corners of the screen. If it's red, you're way to fast. Negative numbers mean you're underexposed and it will be dark, positive numbers mean overexposed and too light. If you can get within +/- 1 you should be able to get a decent print.
You might also want to set the IS to panning mode for Spectromagic since you'll probably end up following a moving float and you don't want the IS to compensate for you moving with it.
It also helps to practice holding the camera very steady; use the viewfinder instead of the LCD, not jerking the shutter button, etc. I've heard it referred to as being "sniper steady" on other boards ... it's what I've been aspiring to!

Lay off the caffeine if you're going to be taking night photos with a P&S!
Also, shoot a lot! A lot of your pictures will be blurry or otherwise messy, so it helps to have lots of shots to pick the best ones.
We S2/S3 users aren't going to consistently get great shots like the DSLR-crowd, but we can certainly get nice ones.