GC in the winter is awesome!! South rim is open all winter. The cool thing is, unless you are hiking down into it, you pretty much stay on the edge and are near multiple hotels, restaurants, and bars.
This is from last November(2015). We got a room at Maswik lodge and did Thanksgiving in the El Tovar dining room.
It snowed on us the second day.. this was looking down into the canyon.
The wife and I
Half sunny, half snowy from the Lookout tower
Sedona would be awesome too. I would stay up Oak Creek Canyon like the Junipine Resort, or you can stay in Sedona proper. Bring a 4x4 or go on a jeep tour. There are a few VERY good restaurants there. We like Rene and Creekside.
Might I also suggest Cottonwood. They have to very very nice boutique hotels(Iron Horse Inn and The Tavern Hotel) and tons of wine tasting within walking distance as well as wineries near by off of page springs rd.
With a week, you could do both places very easily as well!