
At 6 months old your talking about a canine baby who only knows who to play like a dog, this involves very rough games of tugging, growling and biting.
A puppy doesn't realise that a human being isn't as tough as another puppy/dog and can easily hurt a child quite unintentionally.
Not having see the aggressiveness that you describe (which may simply have been mock aggression as in play). You do not say that there were any injuries, and even with a 6 months pup intent on hurting, these would have been considerable to a two year old.
If we are talking a nip due to over excitement I would not be overly worried other than upping my supervising and training of both.
This should involve insistence on calm behaviour, no running about and excitement while in each others company.
they both need to learn self control.
When my children were small I decided that the best option was to fence part of my garden off that meant the dog/s were not able to sue the whole garden. When the children played or had friends around they played in the back away from where the dog/s had access. This also meant that the dogs did not poo where the kids played, and I had the dogs in the largely paved/concreted area that means cleaning up was easier.
Children now grown up and left home, but the area is still fenced off, and the dogs only come up the garden on invitation, helps with poo patrol, and keeping the house mud free.