Chris,
I just ran my three day/two night "Lost in the Serra"course with four adult students. These guys ranged from 23 to 40 years old and only one of them had previous wilderness experiance (Brazilian Armored Infantry). The other three had never set foot off the pavement.
The only water carriers I gave them were US Army canteens and two of the Galão de Emergência, water bags for bulk water.
They did great with them. In all they were carried full over a total of about 8 km of dry scrub country. Each pair of guys was responsible to maintain their water bag full and secure for the entire trip. I gave them no special instructions, I just told them that if their bag rips they would have to repair it with tape and hike back down to the valley bottom and refill it. That was incentive enough to keep them paying attention.
I had platypus bags and an extra water bag as back up in case of total system failure. We had a great time. Mac