I lived in Boulder for 15 years and had a very good friend that lived in Estes, visited often and also events there. I LOVE Estes. I never did it but I think you can have a meal at the Stanley Hotel and just a visit is worth the time. The view from the deck is stunning, especially if you can hit it at sunset. Maybe worth staying overnight there? I am not a big "shopper" but love the shops in Estes, being lots of gem and minerals, fossils, antiques, art galleries, food treats and the usual touristy stuff. Beware though, you will have tons of tourists to fight your way through any summer days. But still would be worth at least 1/2 to one full day in town.
You can do "the big loop, which takes you all the way through RMNP over Trail Ridge Rd, down past Grand Lake and Lake Granby on the west side, a long drive but you'll get your fill of the big mountains.
One of my favorite things in the region was to go to the hot springs pools in Eldorado Springs, west of Denver on I-70. Beautiful drive through steep canyon to get there.
You did not say how much time you have but Rocky Mountain National Park is just a hop, skip, and a jump from Denver. Neither my wife and I are into shopping at all, so I don't know if Estes Park area meets your wife's shopping criteria, though. Of course just a few hours west of Steamboat Springs is Dinosaur National Park and Flaming Gorge National Recreation Area. I really like both, but RMNP is probably more photogenic unless you are lucky enough to get commercial rafting reservations.