On a FF, no, I think that would be OK. But I think part of the outcomes will be dependent on your location. More specifically, how close your are to the subject/focus point, especially in relation to the background (wanting to isolate foreground against background). If you take shots at an angle, while the parade is still coming towards you, you'll get a totally different type of shot than waiting for the subject to be right in front of you. It'll be a function of the angle of view of the lens. When the subject is a little farther away, you'll be including secondary elements on the sides, top, and bottom, that provide more context.
OTOH, you run the risk, if some of the floats get too close, you won't be able to get everything in; moreso from top to bottom with the 50. Some of those floats are tall. Some are VERY long. I was looking at some shots I had from 2001 with an Olympus Stylus Epic (fixed 35/2.8). Sure it lacks reach but I've got a fair FOV and it's not just a snap of a single snowman:
Then again, I waited too long and cut off both the top and bottom of the float here (and this was 35mm):
I think it's very doable with a 50. But I'd choose somewhere around the base of the stairs of the train station or City Hall. Maybe near the curve between the two. And then maybe move around between those two points. Definitely the later parade in hopes of a reduced crowd.