Colorado really does have a lot to offer. You could spend a weeks worth of days and nights on the computer and in trail guides researching what you want to do, and you will most likely plan too much or overwhelm your trip plan.
Here's my suggestion:
1) get to Colorado.
2) Enjoy the scenery and do the touristy stuff, you can stop at hotel lobbies and even some restaurants and pick up brochures for those things.
3) while you are out, stop at a book store (Barnes and Noble, Books-a-Million) and pick yourself up a copy of the Charles A. Wells "guide to Colorado trails". This book is extremely useful, even to those of us that live here, and has numerous trails listed for whatever region you happen to be in. The trail listings even have descriptions and pictures.
From this you can plan day trips, or a full fledged camping trip with the ability to show the family what they are in for. The books have a northern and southern version that cover the whole state, which one you get is up to you (I say get both).........There are a lot of other books like this, But I highly recommend these books, as they are geared toward the offroad enthusiast, while some of the others may be more hiker or backpacker friendly.
By the way, Of all the things Colorado has to offer, water is the most difficult to come by, and will often be the most crowded areas with the highest restrictions.
Don't know your timeline, but you may be able to order these before you get here:
Southern region:
Amazon.com: Guide to Colorado Backroads & 4-Wheel Drive Trails, 2nd Edition: Charles A. Wells: Books
Northern region:
Amazon.com: Guide to Northern Colorado Backroads & 4-Wheel Drive Trails: Charles A. Wells: Books
Interstate 70 is the dividing line
Good luck!!