Ride from Breckenridge --> Frisco --> Copper Mountain --> over Vail Pass --> to Vail. Stay the night in Vail and return. Great summer rates, absolutely beautiful country, Vail Pass is 10,600 feet, Breck is about 10,000 feet and Frisco is about 8,600 feet. From Breck to Vail is about 45 miles. Yes, somewhat challenging, but my wife, at age 65, can do this.
You would really enjoy and remember this ride. All paved bike paths. No cars to scare the wife. In fact, the bike path is the only alternative to the freeway, where bikes are not allowed.