We all travel differently and at a different pace, that's what makes each trip unique. It's great to get others thoughts, look at it from different angles and go with what works for you and the family. Including everyone (Kids as well) in the planning means they can pat themselves on the back on a job well done but can't blame you if it gets too much! (Win win)I know that some will say it is perfectly achievable whilst others will say it is still too rushed and I have ignored all the advice.
The trip looks perfectly doable to me and you have a good idea of what is comfortable for you as a family now. ;-)
If you're not running too late and have a packed lunch, Goosenecks has sheltered picnic tables with a cool view!
I have no idea of what Telluride might be during the Jazz Festival but it's still a a great drive from Cortez up through Dolores and Rico to Placerville and onto Montrose. Telluride is off CO145 so driving through shouldn't be a problem but it gives you the opportunity to turn off and take a look. Between Durango and the Sand dunes you could do a quick stop at Pagosa Hot springs.
From Pikes peak it doesn't add much time to go from Woodland park north on CO67 through Decker and continue up through Aspen park which is a pleasant drive and (imo) nicer than going back to I-25. If it wasn't for the game at Coors field I would of suggested going towards Estes park and just visit Denver after RMNP. Estes park is a good location unless there are cabins available in the NP(?) around Morraine campground. The walking around the Bear lake area is great and for all levels. If you have time, driving the Trail ridge road is a great adventure!