Are you and your group experienced winter travelers on other peaks ?
I hiked Marcy last February or March on snowshoes from ADK Loj via the most direct route (Van Hoevenberg trail). Conditions were ideal that day, trail was broken and skies were blue bird, although there was a crust of ice on top of very hard packed snow above treeline making crampons very helpful).
It was in many ways easier then summer, it took about 8 hours & change RT from the Loj. My guess is this is always the easiest route.
Also from the Loj you have option of going by Avalanche camps & pass, Lake Arnold and approach via Feldspar brook to Lake Tear. I would guess this is the next easiest? Given this is the easiest access to Gray and Skylight, I would guess there is a good chance that this trail would be broken if a weekend has passed since the last dumping of snow. I hiked Colden about 1 week before my Marcy hike last year and the trail was broken all the way to Lake Arnold. I did not check or recall if it was broken beyond that as I turned on the main trail up Colden.
Then there is the approach from the garden. This is longer but I know the trail is well broken out at least to John's Brook Lodge, very popular camping around that area with numerous other popular peaks to attempt with a base camp there.
Elk Lake approach seems to me like it would be a real back country adventure, as it is really long even in summer. I have never been back there in the winter, my guess would be you would be breaking trail most of the way. I would be impressed by a group that could do this in 2 days. I would not recommend this unless your group has allot of winter back country experience and are in really good physical shape, I find trail breaking several times harder & slower then walking on a broken trail. Hopefully some with experience in this area in winter can give better info on it.
So if it were me, being pretty lazy, and not really a solitude seeker, I would take the the most direct route from the Loj. But it would depend on my and my group's objectives.
Sorry for rambling, hope this helps.