I think canning the water is a great idea and its not as time consuming as canning food would be. All you are doing is pouring the water into the jars and processing. You keep the pan of water boiling and you could just keep doing batch after batch.
I buy all of my extra lids at walmart, they are not expensive.
As far as store bought bottled water goes, I am not that confident that it is any healthier and all that plastic is bad for the environment.In fact a few very popular brand name companies get the water from the municipal supply like everyone else and supposedly purify it, not all of these contaminants are removed from the water and you would be surprised what is in that expensive water everyone is carrying around.
I would like the companies to come up with an alternative to those plastic bottles as the majority of those bottles do not get recycled.
I digress, but anyway, I really don't trust the bottled water.
Aside from their water not always being the purist, the plastic is a BAD idea.
The plastic is bad for you, especially if it heats up. If you store a case in a place that gets warm or you leave a bottle in the car or outside while you are working, the plastic is leaching bisphenol A (BPA), into the water and slowly poisoning you.
I have read up on this alot as I head up a biomedical resource group in my area.
This link below is a great resource on this topic.
I think the canning is a fantastic idea.
http://www.rd.com/your-america-inspiring-people-and-stories/rethink-what-you-drink/article51807.html