Hello and welcome to the RTA forums !

I personally prefer a loop trip rather than an out and back type vacation as you tend to get to see more things. Much will depend on how much time you want to dedicate to driving and how much time at any one place. A small Denver loop could have you make your way to the town of Estes Park and check out the Bear Lake area of RMNP which has lovely scenery and everything from a stroll around various lakes to strenious hiking. You could then drive across the park on the Trail Ridge road [providing there are no storm closures] to Grand lake. Allow plenty of time for the drive, the views along this highest continous road in the US are wonderful ! After this you could start to make your way towards Manitou Springs where close by you will find Pikes peak and it's cog railway, [ driving is an option but not for everyone] Cave of the Winds and Garden of the Gods. On the way you could choose various routes, one of them would include a visit to historic Leadville and possibly The Royal Gorge bridge near Canon City. The whole loop could be driven in a day and a half so you will have a nice amount of time to enjoy the sites along the way.

All the roads are paved, but you are going into a mountainous region and it will include twisty sections in places, such as along the Trail Ridge road, but for an experienced driver I would class it as easy enough. At least for a driver who does not have a huge fear of heights.