Understanding Layne's and Sentry's "relationship".... you might want to limit Sentry's influence on Buford when Layne is there.... interaction with Sheba and Buford with Layne would be a benefit... but if anything came up that Layne would have to take care of them for any reason, dealing with 2 accepting, FRIENDLY to the owner's son, dogs, would be better than 2 that don't like him. Honestly, I get Sentry's reluctance... but it is not a good thing for him to be promoting his dislike to a puppy that has no reason to be afraid of or aggressive towards your son. It is enough that they are protective of you... and good that they are taking care of THEIR charges... and Sentry is never going to like Layne as he is a threat to what Sentry considers his flock/family.... through no one's fault... but it would be better that Buford is not influenced that way for no good reason... and he needs to accept that Layne is just fine... as Sheba does......