Michelle,
Oooohhhh, that's a tough one!
And yes, planning is often more fun that the vacation itself for me too!
Consideration 1: Park Crowds
The park crowds are very low during all three proposed weeks. Perhaps a shade lighter in December, but pretty low in all cases. Not much of a helper in deciding when to go.
Consideration 2: Decor
So in December there is that wonderfully festive Holiday decor. But in October you have the fun Halloween vibe. I would give the edge to December, but again a close call.
Consideration 3: Weather
I have been in December when it was PERFECT, but have been there when it was cold and not so nice. The edge goes to October here, with the sooner the better for slightly warmer temperatures.
With a very close race, I would go for a trip in this order;
- 3rd week of October
- 4th week of October
- 1st week of December
But honestly, they are all great times to go!
Have a magical vacation!