[fbkeays]

As mentioned before, throw out or wash anything the pup slept on or chewed on (stuffies, etc) in hot, soapy water with bleach. Spray the area of the yard with 10% bleach/water solution. It has to be fresh, so only make up what you are going to use right then. The parvo virus can live in the envirnment for a year or so if given the right conditions.
Wash your clothes and shoes of everyone that was in the house and has been worn since the puppy was there.
It is VERY possible that your 6 month old puppy is fully vacinated against parvo. A shot given 3 weeks ago is effective (assuming he has a normal immune system). The reason why younger puppies get several shots is that no one knows exactly when mother's immunity wears off and the shots take effect. If a shot is given while the puppy still has his mother's immunity, the shot is effectively neutralized. One shot is enough as long as the timing is good. Being 5 months old, the timing should be good.
I would also wash the dogs in as warm a water they can stand with lots of shampoo. Rinse well.
Keep an eye on their eating and drinking habits and their energy level. Watch them poop to make sure the poops are normal and smell "normal".
More then likely, your dogs are fine. But being paranoid is not a bad thing. Good luck.