From a little north of Denver, I drove to Co. Springs, drove around a bit, went to Pike's Peak and through Garden of the Gods, and drove back in the same day. It was an easy day trip for me, so you might keep that in mind, although some from the COS area may provide you reasons why you would want to spend an entire day there.

Trail Ridge Road may or may not still be open; whether it is will likely depend on whether there have been significant early fall snows. Even if you can't drive all of the way through the park on it, you should be able to drive up it a fair amount and then walk further past the closure on the road. Though if it is closed due to early snows, expect the weather on the portion which is open to be chilly.

You will probably be past the peak of the autumn colors by that time in the Front Range, but if not the drive from Estes Park due south through Black Hawk should have some nice colors.

FWIW, consider combining days 6 & 7 to give yourself a night in Boulder or Estes Park.

For driving around RMNP and the rest of the Front Range, I would try to get a car or SUV with a V6, not a V4. There are enough significant hills that a lot of V4's may struggle and do a lot of switching between gears.