Thanksgiving on the Colorado Front Range is going to be variable - though you can likely get a reasonable idea looking at weather forecasts right before Thanksgiving. Have a backup plan in that case. Also shorter hours of daylight and early darkness at Thanksgiving will keep the days shorter. You should be able to figure out in advance how well cycling ~60+ miles with dogs will go and whether you can do this in two days (or four round trip).

In 2008 I was living in Fort Collins. The State Democratic convention was in Colorado Springs on May 17th, 2008 so I decided to cycle there. I rode to Longmont (actually Del Camino exit) on Thursday evening and then rode the rest on Friday. I took a pretty direct route through Denver (something silly like Federal) and then stayed west via Sedalia and Palmer Lake to Colorado Springs.

So it isn't ideal time with early darkness, morning cold and weather means you'll need to keep a backup plan if you still visit Colorado Springs. However, once you've gotten south of Denver the cycling is a bit nicer and it is a good way to get into Colorado Springs.