Well, it is hard to tell you exactly what settings or lenses, because it depends upon how close you can get, etc. At that time of the day, you will get some harsh shadows (direct overhead sun), so you should position yourself (as much as possible) with the sun at your back so that you are photographing the lit side of the subject. If the sun is on the other side of what you are shooting (meaning you are seeing the dark side of the person/float/whatever) the camera will have a hard time metering, and you will likely get a silhouette with no features. The two ways to control that are to either set the camera to manual exposure and take a few test shoots (adjusting exposure after looking at the image in the lcd), or to set the camera for spot metering.
As for camera modes, I would probably shoot in Av, but if you aren't rally sure about exposure settings then use the program (P) mode. For a sunny day, you will have plenty of light for slow moving subjects so set ISO to the lowest setting and the aperture to f/8 (if in Av mode). If it is cloudy, you should actually get better images, but you might have to up the ISO to 400. For AF modes, I would think oneshot would be best. Also be sure to set the white balance to match the conditions: sunny if it is bright/cloudless, and cloudy if it is - well - cloudy. If it is a partly cloudy day, then I would suggest auto white balance or shooting in raw - because in raw mode you can set the white balance to match each shot's conditions in your image editor. If you are in the front row of the parade route, then your existing lens should be fine. If you will be shooting from further back, then a longer lens would make sense to have with you - something like the 55-250.
All of those settings assume that you are talking about slow moving things like parades, speeches, monuments. If there are flyovers from fast moving aircraft, then your 18-55 lens will not be long enough for flyovers anyway. If you get a longer lens, then for the flyovers I would set the focus to AI servo and the camera to Tv - with a shutter speed of at least 1/640. To get thst speed, you will have to up the ISO.
Current: 5DM3, 6D, 8mm fish, 24-105/4IS, 35/2IS, 70-200/2.8IS, 85/1.8, 100-400/IS v1, lensbaby composer with edge 80, 580's and AB800's
Formerly: 80D, 7D, 300D, 5D, 5DM2, 20D, 50D, 1DM2, 17-55IS, 24-70/2.8, 28-135IS, 40/2.8, 50/1.8, 50/1.4, 70-200/4IS, 70-300IS, 70-200/2.8, 100 macro, 400/5.6, tammy 17-50 and 28-75, sigma 50 macro & 100-300