Big state, lots to see and do; suggestions are easier when we know what YOU like to see and do, when the trip will be, etc.

Do you like National Parks? Do you like Cities, Museums, art? Do you plan to go in summer or winter? Ski? Mountain Bike? History/Mesa Verde? How much time do you have? When do you plan to go? Trains-yes several good trains in CO? Spas? Hot Springs?

You see what Debit is getting at? We have to know a bit more.

And maybe look at a couple of threads that are already here and get some ideas to discuss. Start with "when".

My tip is to research the state for the places that interest you most. Then do NOT overdo the driving or try to see too many places. Focus on a section of the state to explore.

I think a lot of people do not realize how long travel times can be for mountain driving. And a drive-by vacation is a waste IMHO.

Choose from Aspen, or Steamboat, or Crested Butte, or Telluride, or Winter Park areas. . .

There is much to see and do in Colorado. Don't overlook Rocky Mountain National Park and the drive to the top of Mount Evans: http://www.trails.com/tcatalog_trail.aspx?trailid=XFA110-014

HTTY

I'm with Happy. Rocky Mountain Park is a must. Steamboat, Crested Butte, Teeluride and Winter Park aren't really unless you are choosing a ski area.
Aspen has something to offer all seasons, and Glenwood Springs is a good stop.
And sort of to the contrary, I am often surprised at how "close" things are to Denver--2 hours in many directions offers a lot to see.
AND don't forget Denver, particularly with children. Lots to do.
But we do need the season.

You might not think of Colorado as a place for a waterpark, but Denver does have a decent one. I would do it if I were there in July or August when it is warm enough for it. It was several years ago that we were there, so I assume it is still there.

Here's a tip that's independent of where or when you wish to go. We took our Chevy Tahoe out there from Illinois a couple of summers ago. We had horrible car trouble West of Denver. The car wouldn't accelerate on inclines and got to the point where the engine would stall out on idling.

When we got to out destination (Beaver Creek), we took it to a mechanic, who said it was just suffering from too inferior a grade of gas for the altitude. We switched to a higher grade while there and it was fine.

Who knew? There's a reason we're called Flatlanders here in IL.

If you are flying into Denver, go to Red Rocks. Other places to check out is Rocky Mountain National Park, and Garden of the Gods state park in Colorado Springs.

http://www.redrocksonline.com/

Golden is a nice walking town with a lot of history since it was the capitol of the Colorado Territory. http://www.2hourvacation.com/ and The Fort - also on the west side of Denver has an interesting history and unusual food like Bison Eggs and Tequila Citrus Glazed Salmon, but not inexpensive. http://www.thefort.com/

The Durango and Silverton Narrow Gauge RR. Has great scenery that you don't get from the car, and the driver can look to his or her heart's content.

"I'm with Happy. Rocky Mountain Park is a must. Steamboat, Crested Butte, Teeluride and Winter Park aren't really unless you are choosing a ski area."

Not true.

The resorts vs RMNP. Just depends on what you want to do. Most of the resort have ski lifts for bicycle, disk golf, alpine slide, spas, etc. The resorts definately have an outdoorsy feel, of course RMNP has a bit more of that feel.

AS far as I can see we have NO idea when they are going or what they are interested in. We could just go on and on. Maybe the ski resorts are "just right". Maybe they would like to fly fish. Maybe maybe.
Sand dunes, Mesa Verde--who knows.

The resorts I mentioned are located in gorgeous country where there are lots of summer activities like music festivals, art shows, fishing, rafting, etc.

I know that. We don't know what they want to do. We don't know when they are coming. I do think some are more central with the same possibilities and close to other possibilities--like Breck, Aspen, even the dreaded Vail.