Denver to Mt. Rushmore to Yellowstone to Denver

Hello. I am new to this site. My family (mom, dad, two small kids 6 and 9) are flying in to Denver in August and plan on the following itinerary. Other than the obvious big attractions are there any "must see" off the beaten track stuff to see? Here is my planned route (pretty set in stone at this point, since we are only 2 weeks from departure). We are trying not to have any killer driving days, and want some down time, but any suggestions to change itinerary or sights to see would be much appreciated!
Thanks!
Day 1- arrive Denver lunch time from NY, drive to friends house about 1 hour south.
Day 2 -sight see
Day 3- depart some time for Scottsbluff, spend night
Day 4- Arrive Rapid City -Mt. Rushmore?
Day 5- Badlands tour, Wall Drug, back to Rapid City
Day 6- Deadwood (any suggestions?)
Day 7- Depart for Wyoming, Devil's Tower, Spend night in Gillete
Day 8- Drive to Cody, spend night at Irma Hotel (arrive in time for gun fight)
Day 9 -Arrive at Yellowstone in morning- two nights
Day 10-Yellowstone
Day 11- drive back through Wyoming stop for night in Rawlins
Day 12 -back to Denver area
Day 13- Fly home

Welcome aboard the RoadTrip America Forums!

The route you've laid out will make a wonderful RoadTrip for your family. There are always more things you can add but then you eventually have to find the balance between overloading your vacation past the point where it's fun vs. missing something you all would have really enjoyed. Only you all can strike that balance. So you'll have to decide if any of the places I'm going to note fit in with your interests and schedule. There are no 'must sees' anywhere ever. There are several other great sights in the Rapid City area including the Crazy Horse Memorial, as well as Wind and Jewel Caves, and you might be able to fit one of those into your time in that general area. Rapid City to Cody is only a 250 mile drive so you should have time, if you want, to take the short detour north on I-90 from Sheridan, WY to Crow Agency, MT to visit the Little Bighorn Battlefield. And on the way back to Denver from Yellowstone, there are a few less well known stops that might help break up the drive including the National Bighorn Sheep Interpretive Center in Dubois, the Fremont County Pioneer Museum in Lander, the Wyoming Frontier Prison Museum in Rawlins and a couple of national wildlife refuges - Bamforth and Hutton Lake - in southeast Wyoming.

AZBuck