We are going on the 10th this year. We went middle of Oct 3 years ago and on Octover 31 last year.
To be honest, even though it was sold out I didn't feel that Oct 31 was really that crowded. We had minimal wait on all rides and could see all of the characters and candy.
We did Space Mountain 3 times back to back with no wait.
I wouldn't worry, the earlier dates are usually less crowded.