Well, so far so good with our new pup. He is just over 9 weeks and doing well.
My question is this...
We have a 5 year old male Boston Terrier that is starting to warm up to the pup. They get to going at each other in a playful manner. The Boston definitely dictates when it is time to play and when he doesn't feel like it. If the pup comes up to initiate play with a little bite, the Boston will snap at him let him know now is not the time. The pup gets it and usually lays down and stares at him or goes and finds another toy to play with.
When the Boston wants to play, they go round and round biting playfully. They also like to play tug of war with a rope toy they have. There is a point though when the pup will start growling a little, getting more competitive with the tug and wrestling.
Is this ok or should I draw a line when I think it is getting too rough? It won't be long and the pup will be much more powerful than the Boston (even though the Boston thinks he is 100 lbs and bullet proof

).
The pup has working line blood but is strictly a companion/family dog. I don't want these rough play/biting/tugging sessions to turn him into an aggressive dog.
I have noticed that since they started their sessions that he does not target me or the wife/kids with bites as much as he did when we first brought him home.
Any advice would be greatly appreciated. This is our first GSD and I want to take all of the right steps to make him a good citizen and socially accepted dog.