puppy is shy - is this a deal breaker?

Question

Our baby!   Hi there - First of all, thank you SO MUCH for your time.... What a wonderful service!  We purchase a male St. Bernard puppy from a reputable ( or so I thought!) breeder. We met the mother, who is a therapy dog and seemed very sweet. The father was from another kennel, but we were assured that he too was very sweet.  The pup seemed shy, but he had just been bathed, so we assumed he was a bit traumatized by this.  He was eight weeks old at the time we brought him home. During his first weeks at home, I realized that he was shy of new people and places... He would not approach anyone new without lots of encouragement and treats. He is now 16 weeks old, and through TONS of positive socialization, he seems to truly enjoy attention from people. I still give new people tasty treats to feed him, but he will hurry towards people, and his tail will wag while they are visiting with him. I have been greatly encouraged by his progress. He is also much better with new people  who visit our house, although on occasion he still will not come right up and needs lots of encouragement and treats before he will allow them to pet him.
 I have been working with a trainer that has an excellent reputation, as well as good credentials. She has told me that shyness is genetic and you can never socialize it out completely. I have spoken with the breeder, and he will refund our money, but we must return the puppy. We love our puppy deeply, and I can't stand the thought of returning him, and having him be resold to a family who might not care for him as well as he deserves. Other than his shyness around people, he is a WONDERFUL puppy. He is super gentle with the cat, very gentle with my 12 year old son, he is very mellow but playful. He has been easy to train and is eager to please us.
My question is this:  Should I return him to the breeder now before we spend even more time, effort, love and money working  with him? As hard as that would be, I absolutely cannot have a dog that has the potential to bite and the consensus seems to be that a shy dog has a strong possibility of one day becoming a fear biter. On the other hand, I do not want to assume the worst when he is so loving and even tempered otherwise.  Can a puppy that has shy tendencies grow into a safe, well-adjusted adult?  Again, thank you so much for your time and help... I hope I have provided enough pertinent details!

Answer
I guess I have more questions than answers right now.  Has the puppy ever snapped at or bitten a person?  You say he enjoys attention, so why would you think that he might become a fear biter?

Your shy puppy will never be a social butterfly, but he won't necessarily be a biter either unless you've seen these tendencies already.  

I'd love to see some video if you have the capability of putting something up on YouTube or Vimeo.  

Don't force the puppy into situations that he's not comfortable with.  Don't encourage him to take treats from strangers.  This can put a fearful dog in a bad position - he really wants the treats, but then realizes he's too close to the "scary" person.  There's where you have potential for bites.  Let the dog decide on his own terms that he wants to interact with someone.

Dogs have a keen fight or flight instinct.  All dogs have the potential to bite if they feel stressed enough, but most dogs will choose to flee rather than fight.  Be sure he always has an escape route.

Please get a copy of "Help for Your Fearful Dog" by Nicole Wilde.  There's also a good website called www.fearfuldogs.com that might be helpful to you.

Look forward to hearing back from you.