Rescue snapped at grandson, advice needed. Behaviour

I had that same problem when I first got My JRT and my uncles Husky I almost took it back but it turns out that the Husky was never around smaller dogs and My JRT wasn't around bigger dogs.
Basiclly the problem with it is Bruno probably has never been around a new puppy or anything smaller than how tall you are So with the puppy he'll have to adjust. Although I wouldn't be too sure of that either since I don't know your dogs history or what his behavior is.
As far as the child goes I would keep a very close eye on them until the child gets much older.
No child should be left alone with any kind of dog when they are that young since tragidey can occor such as accidental or none accidental.
I hope with was good advice sorry I couldn't help out anymore than what i know and good luck!