Get a big storage bin, maybe 5 bucks at Target, like this:
http://www.rubbermaid.com/rubbermaid/images/product/2244-blue-mist_sm.jpg
Put the pots in the bin, and fill it to the top of the pots with water..
it will be many gallons, and will not dry out in a week..
and the plants wont mind an unusually high water level for only a week..it wont even phase them..
If you dont have enough "good" water, I would risk using tap water if its only for a week..
then just pour some "good" water through the pots when you get home, to flush them out..
tap water is bad because minerals build up *over time*..just sitting in tap water for only one week wont do any harm..
in a pinch, *any* water (even tap) is much better than NO water..
Scot