Scenery:
Try 34 west out of Loveland, CO, follow it through Rocky Mountain Nat'l Park (lots of camping, you might want to make a reservation) and over Trail Ridge Road, it gets you around Denver ;-) When you get to 40 go south to I-70 westbound. You'll go back and forth over and under the Continental Divide but the scenery will be worth it. More? Take 9 south from I-70 and Frisco over Hoosier pass. That'll lead to 285 south which will carry you to Poncha Springs. 50 west takes you over Monarch pass to Gunnison and on to the Black Canyon of the Gunnison, then Montrose. South on 550 takes you to Durango then west on 160 or take 62 at Ridgeway to south on 145 at Placerville, either way gets you to Cortez. I've driven these roads a few times, just as fun now as at first. Be sure your brakes and steering are up to snuff.
or
Take 119 west through Longmont to Boulder, head north on 36 to Left Hand Canyon and go past a few campgrounds up to Ward, where the office of Mayor rotates among the citizenry weekly (or it did until a couple years ago). Go south on 72 through Nederland and Rollinsville and into one of Colorado's casino districts at Black Hawk/Central City. Central City was a nice historical stop back when... on south to 119 which leads to I-70 west.
Speed:
I-25s to I-76w to I-70w isn't too bad if it's not rush hour. I-70 west to the Grand Junction area and 50 south towards Montrose, Durango and Cortez.
Camping:
Between Cheyenne and Denver, near I-25 are Boyd Lake and Barbour Ponds, both state parks. OK camping if you're just stopping, Boyd Lake is big enough for small boats. If you take 66 West at the north end of Longmont through Lyons and on to 7 south you'll get in to a canyon with a few little roadside campgrounds. In fact, along the non-interstate roads in the National Forests are quite a few nice little places to camp, you should check
http://www.fs.fed.us/arnf/recreation/index.htm for campgrounds, reservations, etc.
Like someone else said: Carry drinking water for all involved, it's dry in a humid year.