Im not an expert but in my experience its really all about training. anytime you have a dog around a young child or baby you need to always be watching very carefully. I wouldn't leave the dog around the baby unsupervised. As for as anything aggressive i wouldn't worry about that. It sounds like your puppy is just trying to engage your son or daughter in play like they would engage another puppy. my 2 year old mix does the same thing with my 3 year old cousin. As far as training goes, I would go to the dog whisperer ceaser millans website. The website is really useful and might have the answer to your training question.