Bad idea. The hike from Yosemite Valley floor to Little Yosemite Valley is up-up-up 2,000 feet. It's definitely not easy. It is difficult without a backpack. It is difficult with a summer backpack. It would be extremely difficult with a backpack filled with winter gear. You (or your wife) may get sick working that hard at high altitudes if you haven't spent time at that high elevation. When dealing with winter conditions, you're going to want to bring extra food in case you get trapped in a storm. If it was snowing, it would make it even harder on the acscent or decent.
I wouldn't recommend snowcamping with someone who doesn't have camping, let alone backpacking, experience. My husband and I took a snowcamping training class through the Sierra Club before attempting snowcamping in the mountains
http://snowcamping.orgThe thing that made me feel the most comfortable and safe was being with a group of people.
Do you have snowshoes? Do you have winter gear? Will you spend some time acclimating to the high altitude? Snowcamping can be very beautiful, but can turn scary fast if you are unprepared. Sleeping in a tent is cold. Bring hand and foot warmers.
If you are still set on snowcamping backpacking with someone who is inexperienced, I would suggest starting from Badger Pass up on Glacier Point Road. Possibly to Dewey Point (you can't camp on the point itself, you have to be back in the woods a bit). There is a beautiful view down into Yosemite Valley, particularly El Capitan, from there. You hike out on a fairly level road (though there are some up and downs which can be difficult if you are not acclimated to the high 8,000 foot altitude). After awhile you go off the road to get to the point. There is a steep but not super long hill before you reach Dewey Point.
You can talk to the people at the ski/snowshoe rental about conditions and other possible places to camp. If you can't make it all the way to the point, you can probably camp anywhere off the trail along the way. Call Badger Pass at (209) 372-8444 for up-to-date conditions or other suggestions on where to camp.
Here is a link with brochure download for marked winter trails:
http://www.nps.gov/yose/planyourvisit/wintersports.htmThey are good brochures for anyone considering outdoor winter activities. The difficulty descriptions are somewhat more geared toward skiers. What's difficult on skis would be less dangerous on snowshoes. It's good to go on winter marked trails because other Yosemite signs are buried by snow.
Booking a trip to ski to Glacier Point in winter is fun if you are in shape and know how to cross country ski. Then you can stay in the lodge at Glacier Point overnight after a LONG (10.5 miles) day of skiing.
http://www.yosemitepark.com/BadgerPass_BackcountrySkiTours.aspxHave fun and ask more questions if you like.
For your own safety, be prepared for the worst-case scenario when snowcamping. Go to well-traveled areas for your first trip, it's still not as crowded as summer.