1st of all, extremely sorry for your loss, however, its great to know that everyone is fine and alright, and no damage was done with regards to injuries or further severe issues.
Airbags get opened / deployed under certain particular conditions and defined set of rules. Hitting a dog at 120 kmph might not be one of them.
2ndly, if seat belts aren't properly fastened, then airbags can bring harm than goodness.