puppy aggression?

Question
I just introduced a 3 month old std poodle puppy to my pack of 3.  The puppy seemed really quiet and sweet to people and other dogs.  I met his mother, who was a little rough, but friendly.  I introduced him one at a time to my 3 dogs.  (2 little bichons and a std poodle.) He was ok with the first two and then snapped/growled at the third who was invading his personal space.  He seemed to get over it and then later was sleeping when the other poodle startled him awake.  He growled and snapped at her.  But, although he was in range, he did not follow up with a bite or a chase.  It was clearly a warning.

Is this normal pack shuffling or is this a sign of aggression to come?  I had no trouble with any of my other 3 but I realize it is a new pack every time you introduce another dog.  He is the only male.  I am tempted to overlook it because it was a busy/ stressful day for the pup but I don't want a puppy that is inclined to bite first and ask questions later.  I do have young children who live with me, perhaps I am oversensitive to dog aggression but I have to have a safe dog.  

Also, what can I do to help this situation.  I already love the puppy and would like to do whatever I can to solve this problem.  

Thanks!!

Answer
That's great.  I'm sure you'll be able to have a great dog, and it's nice to hear that you are feeling more confident.
-A