As the others have said, Spectromagic is the night-time parade in MK and all of the floats are done up in lights. Check carefully to make sure when Spectro is being put on because it isn't run every day.
My DS & DD liked the parades, though the times can be tough - the afternoon parade in MK is at 3pm, which tended to be pushing it a bit for my kids if we got to the park at opening. Likewise, Spectro is usually later in the evening, particularly when the park is open later. As they have gotten older, we've had less problems in this regard, but the last thing you want to do is try and cram yourself into a good parade viewing spot an hour ahead of time and have to give it up just before the parade starts b/c the kids are getting too tired and cranky.
As for the shows, it has really been hit or miss with us. A lot of times, I suspect, it is totally dependent upon on the kids' mindset at that very moment. Last year, for instance, they absolutely loved Mickey's Philharmagic but were totally freaked by Honey I Shrunk the Kids.
We have also had to be sensitive to the fact that DS has a real problem with loud noises. Our first trip, we tried to go to the Hoop-De-Doo Review. Five minutes into the show, DS was in tears because they lowered the lights and started the show (and if you've been there, you know it starts out really loud). This also plays into our planning with respect to fireworks - DS loves watching the fireworks, but he hates the noise, so last trip we planned several opportunities to watch fireworks from a distance (i.e. Wishes from the California Grill at the Contemporary or from the Polynesian Beach).