What you are finding on the web is all scary and correct. Do not believe the websites that say they have a cure or natural treatment. There really is no treatment except for the virus to run its course. Treatment is all supportive care to keep the animal hydrated and alive. Keep them separated and yes always wash everything with bleach solution. Where disposable gloves and put feet disposables on also that cover the shoes. never let them in the yard or anywhere else in the house. parvovirus can live months outside in the yard. The older dogs should be ok if vaccinated but I myself would not take any chances. It spreads easily and fast.
The pups probably got it from the shelter which is why I can't understand why they sent them back to your friend. If the puppy that was given away is fine then they got it at the shelter. Not uncommon.
Here is a veterinary link with lots of info:http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/23301.htm&word=parvovirus
This is so sad. I hope it all turns out ok.