Don't get me wrong. I think day 7 is doable, especially since the Cog Railway is in Manitou, before you get to COS. If you can roll by 8:30 or so, you should make it into Manitou Springs by noon, 12:30 at the latest, time to grab a snack. Then up the Peak by Cog Railway (not sure you want to try driving it in October without 4-wheel) and back with plenty of time to get to Garden of the Gods (also on that side of town). After sunset, head on up to Denver.