Okay so, we went to have dinner with a friend today who has just moved back into town. She has many dogs and most of them she's had for years besides two of them. One was a Saint Bernard, sweet as can be and very gentle with my almost two year old son. But while our son was running around, stomping his feet to make his shoes light up, the other new dog (not sure how old the dog is or the breed, maybe a heeler) ran up and bit my sons face. My friend immediately reacted and took her dog outside and felt so bad, but we went ahead and left before dinner was ready because I was just upset and my baby was scared of all the dogs that were still in the room and refused to be put down, and I just wanted to take him home. The bite didn't break skin but I do not feel comfortable bringing my child back to her house after this. Her mother was there and tried to say that some dogs just don't know how to react to children but I feel like that's not an excuse to just brush it off and take that risk again. How can I nicely and respectfully tell a friend of ten years that I can't bring my son to her home? Am I overreacting or underreacting?

Pic of the bite. The two raised spots on in the top circle are from the top front teeth and the mark on his cheek is from the bottom teeth.