I'm pretty sure a couple of beers would stay cool wrapped in your spare insulated gear? Are you already using a pack? Maybe you have a spare light weight down sleeping bag laying around? Of course you'd should be careful unpacking. But, your beer should maintain a relatively constant temperature if swaddled well? Shall we talk about the ideal temperature to enjoy a beer. I've definitely heard that room temperature is best for many Belgian beers? Of course you need to make certain that the bottles are also protected from breakage in your pack. Also, try to not let the bottle rest in a place where you might set down the pack. Ideally the bottles floating somewhere off the bottom or sides of the bag. Avoid carrying the whole six pack. Maybe find a way to have each person stuff two bottles away?

I do find it semi irresponsible to use glass outdoors. Accidents happen and god forbid, but beers occasionally tip over. I completely understand that you have no intention of ever leaving glass behind. But, if glass is broken it may be impossible to remove everything?

I'm sure you know the descents are often where injuries occur? I'm not trying to project negativity, but please watch the step going down.