My family has always enjoyed trips to CO, so can only offer that...after always spending time in RMNP and along I-70...last year the wife and I got away for an anniversary trip to the Aspen area which I highly recommend. The views up high were amazing, was still a lot of snow in late June last year. We also did our first overnight backpack trip to Conundrum Hot Springs...I cannot explain how awesome of an experience that was to soak in 100+ degree pool (all alone for awhile) surrounded by snow capped peaks...9.5 miles from civilization.
Highway 24 from Vail to Buena Vista also offers a lot of great scenery with Holy Cross Wilderness, Mt. Elbert & Massive outside Leadville...and the Collegiate peaks down toward Buena Vista. I was amazed how much the terrain changed from I-70 down to Buena Vista from dense pine forest to semi-arid/rocky terrain...and beautiful lakes all along the way. If around Leadville, I suggest getting down to the eastern shoreline of Turquoise lake...that backdrop across the lake with CO highest peaks...and sandy beach shoreline was fantastic.
Regardless - sounds like you have plenty of options and a great trip ahead - Enjoy! And share some pics!