With the park being closed now on mon-tues.. AND with fall festival going full blast i would expect weekends to be pretty busy now through the end of the year.
With the options of all week, I would think wed-thurs would be great days,, maybe friday.
There will still be some people there, but with school in session this eliminates the "family" factor.
Have a great time, and dont wait until spring.. The Fall festival is one of the best festivals in my opinion.. Christmas festival is great also!
Dont forget if you are going to stay overnite, "we" get a great deal on motel at Homestay Inn. 417-336-2666