IMO, using a flash for the night parades kills the look of the parade. Instead of using the flash, get yourself the Canon 50mm f/1.8 lens. It can be had for under $100 online. Combine that with your high ISO and use this lens at f/1.8 you'll get good enough shutter speeds to stop the action and capture all the great colors.
Here is a shot I took during our '05 visit to
MVMCP. This was using a flash (Nikon N70 film SLR):
This one I took in '07 using the Sigma 30mm f/1.4 lens with NO flash (Nikon D50 dSLR):
In the 2nd picture I also had additional help. There is a nice light coming off the facade of the Diamond Horseshoe in Frontierland. However what you can see more of is the background, in the 1st shot the background is gone. Also the tree. The flash washed out a lot of the stuff on the tree. The flash also flattened the colors. They look more dull. Not as good of a look IMO.
The 50mm f/1.8 lens will have a tighter field of view, but there isn't to much difference between f/1.4 and f/1.8.