Usually, after the 2nd series, they are quite protected. Usually, it's every 3 weeks until they're 16-21 weeks old. If you choose a spot, perhaps closer to the house, where other dogs have not been, it should be relatively safe. Also, parvo (the really dreaded disease) is primarily a puppy disease. It is not as likely that an older dog that fouled your yard had parvo. This is not an exact, cut and dry science, but it is my understanding that this is the tendency.
Another thing....it is vital that you get your puppy out into the world to socialize him, using reasonable precautions, as mentioned above. (no dog parks, pet stores, places which are highly populated by dogs) If you do not get him familiarized a lot with other people, of all ages and sizes, different enviroments, your dog will be fearful and mal-adjusted as an adult. This needs to be carried out before he is 12-16 weeks of age and continued. But he must have quite a saturation (without overwhelming) of steady accustoming of all kinds of things. This window, between birth and about 12-16 weeks is a critical developmental time and if he misses out on socialization, the ramifications are equally horrendous IMO as the risk of disease. You have to take reasonable precautions, but do get him out. Go for social visits to the vet's, let him meet friendly dogs who you know are healthy and you know are friendly. He must not be made frightened of things. All his experiences need to be associated with a happy, pleasant time....treats tied to other people and his "good" and happy behavior etc.
This is also the time to get him used to nail clipping, baths, teeth brushing, handling (pretend examinations) by "strangers" ....the vet. Just anything you think you'll need to do to him later, do it while he's in this critical period, again, making associations pleasant and unfrightening.
He is adorable. I bet you're excited. Good luck.
