Staycation - Denver,CO

In regards to the old ghost town idea... South Park City in Fairplay is an interesting place. It's a recreated old west town with lots of history presented. It's a very do-able drive.

Kind of a long drive, (maybe too long for a 4 day vacation but closer than Moab) but...
I love the narrow gauge train ride from Durango to Silverton. It doesn't go all the way in the off season, but it does run, and in fact the shorter trip can be nice for the kids. Both of our kids loved it.

Mesa Verde... always fascinating.

Glenwood Springs is a favorite.

If you're willing to drive as far as Moab, you could go a different direction and head to Mt. Rushmore. If you go there, be sure to try the Needles highway (great tunnels!) and the Custer State Park wildlife loop... amazing wildlife right by your car! Lodging there is quite inexpensive in the off-season. If you're willing to go a bit off the main path you can see the Register Cliffs where pioneers traveling the Oregon Trail carved messages in the cliffs for those coming after them. You'll be able to touch the ruts from the wagon wheels!

Have fun and let us know what you decide!

What about finding an old 'Ghost Town'? What could be better memories than a roadtrip for Halloween!

We also love Manitou Springs, which is where cave of the winds, and garden of the gods are located. We also recommend Estes Park - they are having a halloween festival - http://www.estesparkcentral.com/viewevent.php?eventid=33

Co Springs.
you can feed giraffes at the zoo.
there's Seven falls and the cave.
there's the fake cliff dwellings.
garden of the gods.
the kids might be pushing the North Pole amusement park for age because its really geared for late preschool/early elementary, but consider it.
there's a new state park on Cheyenne Mountain.
the cog railroad up pikes peak.
royal gorge is not too far and it now has an amusement park surrounding the bridge.
there's a mining museum
hotels are all over the board, ranging from kitschy $50-60 a night in Manitou to the Marriott or Broadmoor so one should fit your budget.
have fun wherever you go!