Camelbak makes an insulated line which helps protect against freezing. I've had the line freeze before when I was hiking at 9k feet in CO but never had the reservoir freeze. Maybe you guys should have waited till the spring, lol. How much water did you carry per person?
How many actual miles did you do? Sounds like there was more camping than hiking/backpacking. (not judging, just observing)
I think you have an Android phone, check out Google My Tracks for recording your path.
I have one of the Outdoor Gear hydration packs but I kept mine in my tent wrapped up in my clothes so it didn't freeze. Dave had his hanging off the side of his pack like an IV bag 
...it didn't fare as well. His other reservoir in his pack didn't freeze though. He brought 2 liters with him as did I. I had a bottle (the purple one in the pics) along with the reservoir. That's one of the downsides of bringing your dog along, have to carry their stuff too. I've been checking out a few dog packs but haven't found one I like yet... and some of them are redonkuously expensive!
We only put in about 7-8 miles total. It turned out to be more of a camping trip than a hiking trek. Now that we know a little more of what to expect we can plan our next trip a better. We're already talking late winter/early spring time. With jobs and kids and family it's a bit difficult to get all of our schedules to mesh. I'm sure there'll be a few solo trips in the future as well but it's always more fun being with friends.
