Dogs have to be taught that a hug is a good thing... their instincts are that it's confinement and something to get rid of, quick. I agree, Atticus looks a bit unsure of that hug.
Does the dog know any tricks?
I'd have your son teach him some tricks. They should be simple in the beginning, so both the dog and your son can be successful.
You can also enroll in a training class, and have your son go along.
Just walking together is great bonding time, too. Try to convince your son to take things slow - the dog is in for some major life changes, and all the new stuff needs time to sink in.
It might be a good idea to get your son a book or video on dog behavior, so he can learn 'doggie communication' and understand what Atticus is trying to say through body-language. Nothing better (in my opinion) than education to help them understand each other and start a great life together.
I'm sure others here will have some good advice to add.
That's a beautiful dog!! Congratulations!