Hi Martin,
The real concern is when going from cold to warm with your camera. (That's where condensation will form.) As you may already know, you'll want to seal your equipment in airtight bags (large ziplocs work great for this) prior to going inside. Once inside, let the equipment warm up to warm temperature while still sealed in the bag (4 or 5 hours) and then you can take it out. Your batteries will be ok, but it's best to always have a fully-charged spare or two, and you'll want to keep those in an inside pocket so they'll stay warm.
Have fun! It sounds like you're in for an awesome trip!
Bryan