for summit night I do not find Camelpacks very usable, it is better to have a thermos with sweet tea and some other bottle with a powdered drink, which you can drink at stops. If you drink a lot before departure, take some and then when coming down again a lot, you will be fine.
The hose will freeze, does not matter how insulated the bag itself is. Every kilo/pound counts and there is nothing worse than carrying frozen water up a mountain (though it might help against the receding glaciers).
If you will use the pack, always blow the hose clean after each sip (blow air into it until you feel no resistance), so that you have no water standing still in the hose at any time. If you forget it once, chances are it will freeze