SpectroMagic has got to be the trickiest thing to get good photos of in WDW, outside of on-ride "dark ride" photos like PotC or HM.
I took a bunch, with lots of different settings, and got the best results with the exposure compensation turned up a little, to show some detail other than just the lights. (Sorry about the large images - the 700-pixel-wide ones just don't show any detail.)
Before the show started, I got a little practice as the CMs warmed up the crowd - this guy was interacting with the boy in the background. ISO 1600, F1.7, 1/90th second, cleaned with Noiseware (as are all of them.)
The creepy lighted-face guys... ISO 1600, F1.7, 1/500th second.
Alice, ISO 1600, F2.0, 1/90th second.
The evil queen, ISO 1600, F1.4, 1/90th second.
Minnie, ISO 1600, F2.4, 1/90th second.
For some reason, the Chernabog float was not running when we were there last month.
If I was going to film it again, I'd again use the 50mm 1.4, set the auto ISO to 200-1600 (instead of the usual 200-400), push up exposure compentation to 1.5 (which these were set at) and shoot in shutter priority mode, 1/90th second. That should be enough to get most parts of the parade with pretty good results (and hopefully some at lower ISOs), though you may still get a little motion blur on fast-moving things like the spinning balls or character's arms.