Hello Deborah and thanks for bringing such a
spooktacular question to the Disney Parks Moms Panel.
I absolutely love
Mickey's Not So Scary Halloween Party and was quite excited when Disney announced early August dates so that yet more foolish mortals could attend this fiendishly enjoyable event!
Even Madame Leota with help from the 999 happy haunts from the
Haunted Mansion would find it rather tricky to try and predict crowd levels, but I would think that Mickey's Not So Scary Halloween Party nights during August may not be quite as busy as those during October and certainly dates nearer to the 31st which of course is Halloween night itself.
My family usually catches the later
Mickey's Boo-To-You Halloween Parade on party nights and yes, they sometimes are less crowded. However, for me the bonus of planning to watch the later parade is that I can usually take advantage of less wait times at attractions during the earlier parade as most Guests are happily watching out for the Headless Horseman!
Plus be sure not to miss either the spectacular
Happy HalloWishes Fireworks or the wickedly good fun
Hocus Pocus Villain Spelltacular Show.
Have a great Disney day.
~ Jane