As others have said, I would go over Shepherd Pass. George Creek used to be open only a few weeks each year. It sucks. I had an unpleasant and unsuccessful attempt on Williamson in January 1995.
All the peaks over 13K in that area are worthwhile. Tag as many as you have time for. Tyndall and Trojan are especially nice. Carillon is trivial from your route. Russell is one of my favorites, though it’s exposed.
Your route takes you right past Upper Boy Scout Lake. I would leave my heavy pack there, tag Whitney as a quick dayhike, and descend directly to Whitney Portal. However, if you insist on hauling your heavy pack up the Mountaineers’ Route, I would tag Muir on the way to Trail Crest.
Finally, class 3 in Colorado tends to be easier than class 3 in California. Descending the west face of Williamson wearing a heavy pack after you came up from George Creek could get pretty interesting. If you use Shepherd Pass and camp in Williamson Bowl, you could tag Williamson with just a daypack.
