My husband and I will be traveling to Colorado in early May- flying Into Denver and staying the first 3 days at the Broadmoor. We will then have 51/2 days left in Colorado in which to sight see and explore before flying back home out of Denver. I know Colorado is a beautiful state with so much to see and explore - looking for some itinerary advice .. start here, drive to here.. see this.. don’t miss that.. next drive to here... etc... We will have a rental car.. Would love to have some suggestions. (I have been to Estes Park - so I prefer to not go again. We love scenery and nature. Thanks in advance!

You may find that rental cars are cheaper in downtown Denver than at the airport. How far do you intend to go out of Denver while staying at the Broadmoor? There is a good light rail from the airport to the Transport Center/Amtrak station. There will probably be quite a bit of snow above 8K' so hiking will be limited in early May.
My favorite trip out of Denver is on the Amtrak California Zephyr to Glenwood Springs. The Glenwood Canyon just east of Glenwood Springs is one of the most scenic daytime views on any Amtrak route. Looking out of the train windows beats driving and watching the road ahead of you on I-70 IMO. There is a good bus service from Glenwood Springs up to Aspen (41 miles). There are several good hotels within walking distance of the Glenwood Springs Amtrak station.

It is cheaper to rent off the airport but in all the years we have flown in and out of Denver it has NEVER made sense time-wise or convenience to do it.
Although you say you have been to Estes Park, have you driven through the Park on Trail Ridge Road? Doing that you could then continue west through the mountains to Glenwood Springs and Aspen.

Hi- and no, probably did not drive trail ridge road.. would definitely be willing to do that.. just trying to make a plan that will work with the time that we have .. with a swoop back to Denver to return home- meanwhile seeing all that we can while there

Going through the Park does allow you to make a nice loop through the mountains. Coming back you can do another loop through Leadville. I'll let the Coloradoans fill that in. We enjoy Frisco for a cute place to stay and with a good selection of restaurants.
Would you like to fly fish for a day? Engage an outfitter in Silverthorne and fish the tail waters of Dillon Dam for BIG trout. Or the Blue River just north of Silverthorne for trophy trout waters.
Lots to do around Aspen and Glenwood. Don't miss the exhibit on the way to Glenwood about the construction of that highway.

Trail Ridge Road is closed until late May, and then only open weather permitting.

If you're interested in beautiful scenery and some whitewater rafting, you might consider heading up US 24 to Buena Vista after leaving the Broadmoor - about a 90 minute drive. Maybe spend a night or two there, rafting and exploring (lots of hikes in the area)

You can then work your way back to Denver via 24 towards Leadville or take 285 towards Fairplay. Lots of options.

While at the Broadmoor, definitely check out Garden of the Gods. Also, if you like zoos, the Cheyenne Mountain Zoo (pretty much right next door to the Broadmoor) is quite a nice zoo—and I say that as a San Diego native.

Manitou Springs is a neat little historic town nearby also in which to while away a few hours.

In Denver proper, check out the RiNo (River North) district (uptown from LoDo), which is a booming area with lots of breweries, art galleries, restaurants and food halls.