Most of the times I've been to a MNSSHP, once the first parade and the fireworks are done, it really starts to clear out, and you can pretty much have your run of the park, and not have to worry about lines for the rides.
I wouldn't think on a Sunday night (the 17th) in the middle of October, it would be that different, but, if your going with children, I would advise to get them some rest during the day, so they can get the most out of the party as well.