Rethinking 2 week visit out West

We did a 2 week "front range" loop in 2010 and thoroughly enjoyed it - coming from Illinois, so about the same distance as you. 4 nights at RMNP - great scenery & hiking, had an awesome site in the C loop of Moraine overlooking the valley where we would just sit & relax in the morning (unusual for go-go folks like us). 4 nights at Mueller S.P., used as a base for Colorado Springs, Pikes Peak, Garden of the Gods,etc. 3 nights at private CG in Canon City, Royal Gorge & rafting. 2 nights at San Luis Lakes S.P., hit the Great Sand Dunes N.P. (a don't miss!!), train ride out of Alamosa to a cool amphitheater in the mountains with an afternoon bluegrass extravaganza headlined by Michael Martin Murphey (remember "Wildfire"?). Great trip, enough time in each spot to actually be relaxing, even the teenagers ended up having a good time (whether they wanted to admit it or not). Starting at RMNP and going all the way down to the Grand Canyon would probably be too much driving for the time you have, pick one or the other.