Great idea. I have driven the PP road (not on July 4th) and taken the cog-railroad. It is much more relaxing to take the cog railroad. You can catch it in Manitou Springs.
The Royal Gorge is great. You can drive across the bridge or walk it. The bridge swings a little but it is interesting to watch.
When you are in the Denver area, drive to the top of Mt Evans. It is the highest auto road in the U.S.
I once had a captain who, after leveling off at 12,000 feet asked me "Ever been this high before kid?" I replied "yes but my feet were still on the ground." Pikes Peak is 14,110 and Mt Evans is 14,220 feet.
I don't know how much time you will have but while in the Springs area, check out The Garden of The Gods and the Air Force Academy.
Once again, depending on your schedule, a trip to Central City west of Denver is always interesting.
[This message has been edited by airplane driver (edited 7/27/2009 10:07a).]