I have a 6 month old Shepperd mix mostly Shepperd we adopted him from a rescue shelter he is a sweetheart with my two very active toddler ages three and four .I usually have lots of play dates and have family members with children come over to visit.Since we have gotten him our visit are short and not sweet and I even attempted to have have a sleep over with other children and that didn't go well either we had to keep him in his crate or other room because of his barking and attempts to bit he just recently chased neighbor hood children down the street and attempted to bit them because my daughter got to the front door before I did and let him out. He's not violent with us how do I get him to be friendlier to other people? HELP

Your dog does not see humans as his superior, he thinks he owns some of them and is their "alpha." I can't tell you in the space allowed how to train your dog but he clearly needs training as you do too. I am not trying to insult you as many people just get a dog, fed it and pet it and sometimes luck out with a dog who does not go after anyone. There are many dog training experts out there you should study, Cesar Millan for one. PS for example, never open the door and let the dog go out. You step out to show him you are first, the boss and he always follows you, never leads you.

Do you walk the dog around your neighborhood and go to parks with your dog? Sometimes you need to allow the dog to see that there is a difference between consent and protection from strangers. I agree with ballengerb in that you need to work with the dog more and get some training if you can't do it yourself.

Socialization is key with dogs. If a dog is not properly socialized with children and other dogs there is a tendency for it to be aggressive.
An example would be, I know someone with a female bulldog, only a few people were allowed around her, she was not out with other dogs etc and now she is a temperamental vicious dog. She cannot be let out with other dogs at all, she will attack them and 90% of people can not touch her or go near her at all.