I spoke with REI in Albuquerque earlier today. The lady I talked to indicated that no reservations were necessary. They apparently have a ton of snowshoes, including several varieties. Even the more expensive ones were pretty inexpensive. They were also OK with a slightly open-ended rental period, given the uncertainties associated with this kind of event.
I have noted that there are differences between snowshoes and those differences can mean the difference between "post-holing" and staying up on the surface of the snowpack. Some are definitely better than others. Been there, had to have a railroad guy dig me out once when I was at White Pass. Of course there, we had like 20 feet of snow at White Pass. At Cumbres Pass, there are more like 4 feet. With a season's worth of heating, cooling and settling, the snow on the pass is probably pretty dense.
I would also advise folks to slim down their gear as much as possible. Pack light. Unless you're shooting video, leave the tripods in your suitcase. They are predicting partly to mostly sunny weather for this weekend. With snow on the ground at ISO 200, you're going to be shooting 1/800th or higher, even at f/8. Getting sharp images will not require a tripod. Besides, tripods definitely increase the chance of someone getting body parts or their cameras whacked by someone else's tripod.