I was lucky enough a couple of weeks ago to do attend a weekend program at Fort Ticonderoga on Lake Champlain in NYS. When we walked into the fort at 9 AM the temperature was a whopping -5 F and it didn't get much better throughout the day. This wasn't my first time in that kind of cold in period clothing so I knew what so many other people already know...wear wool. I had on a pair of heavy wool long socks, wool breeches, a wool shirt, wool short jacket and, when it really got cold, my wool coat. I also wore a pair of double knit wool mitts and a Dutch mutsen hat (like a ski cap). That evening when I laid out on my pallet (they let us sleep in the original unheated barracks) I kept all that on and slipped under 2 wool blankets. On the whole, it was a warm and toasty evening. I really hated getting up in the morning. I don't know what the interior temperature was in the barracks but I've used this same set-up for winter camping trips in NYS and have been fine down to near 10 F.
All that being said, I commend you on your trip. I'm almost 62 and usually have a tough time finding folks who want to go out overnight in the winter so it's great you have a group to go with. Keep at it. We only really get old when we stop doing the things we love.
That's all for now. Take care and until next time...Be well.
snapper