Tim, here are some thoughts I would offer that have served me well in wintertime Baxter (beyond what's in chocodove's list above) ...
- Most cabin folk I know filter their water. Good practice though, once filters are wet, is to take care to protect their elements from freezing, which might have the potential to cause enough damage to enable pathogens to pass through. The Katadyn (great brand name for a Baxter trip!) Hiker Pro, however, will not be damaged by freezing temps, so long as you're careful to pump out as much residual water as possible after use, and refrain from trying to pump the filter until it's completely thawed out. UV is also an option since the stream or pond (depends on the site and cabin) water you'll be using is pretty clear, but it is more prone to technical failure than the other options. Iodine? Yeah . . . I don't even like the taste of Aquamira (chlorine dioxide). But if you do go chemical, don't forget that the cold temps dictate a much longer steeping time.
- The wood stoves work well, and the park provides ample supplies of pre-split firewood within reasonable walking distance of the cabins. Depending on the cabin, you can achieve temps in the 70s and even 80s. Most groups shoot for low-mid 60s, esp for sleeping. If no one in your group is familiar with their use, the only potentially confusing items are the adjustable air intake ports on the door (you use this to control the fire intensity - and hence rate of fuel consumption - by regulating the amount of incoming oxygen), and the flue flap. When you're getting a fire going, and/or when opening the door to tend the fire, make sure the flue is open; if you forget this, you can flood the cabin with a belch of smoke. To minimize the loss of heat to the outdoors, close the flue once you've got a good fire going. Don't forget that the stove and the flue are HOT. Don't let your skin or a wayward taffeta puff inadvertently come in contact for even the briefest moment. Also, the park provides a shovel, bucket, and outdoor trash can for the stove ash. You may need to use these to ready the stove upon arrival, and it's a courtesy to clean out the stove when departing.
- You won't need the -20 sleeping bag, as it's unlikely that the overnight temps in your cabin will drop below 40 unless you want them to. A 20-30 degree bag is good.
- Bring a Coleman lantern mantle or two with you. The cabins use these. Usually there's a spare in the cabin, but it's a good idea to be prepared -- they're extremely fragile and vulnerable to breakage via human error (accidentally touching them when attempting to light the lantern).
- It's a good idea to have at least one mountaineering shovel in your group to deal with clearing out the cabin area in the event of copious new snow. I've seen snow shovels in the cabins some years, but earlier this month, for example, our cabin didn't have one.
- To the extent that you're providing for "down" weather days in your plan, bring things like cards, Bananagrams, etc.
- I like to bring 'happy hour' food (munchies, cheese, etc) and beverages (pick your poisons - hot choco, miso, alcohol, etc) in addition to classic winter hiking rations. Especially appreciated by folks during down days.
- Bring a weather band radio unless you've got a sat-link for your smartphone. A great way to get updates mornings and evenings in the event you find yourself in a dynamic weather period.
- Bring lots of line to string around the cabin for clothes drying.
- If your plans will take you above tree line, carry a rope (I would recommend 20m of 6mm Perlon) for rescue purposes. On Abol Slide a couple of years ago, one of the guys in my group took a serious fall, resulting in bad head trauma. The rope was key to getting him safely down the slide in his injured state to where rangers were waiting with snomos.
- You didn't mention any questions around your mode of transport from car to camp, so I'm assuming you're all set on that front.
Hope this helps . . . don't hesitate to follow up here and/or via e-mail as appropriate.
Alex