XF-KID, glad to hear that you weren't injured. Sometimes with car/deer type encounters, drivers wind up with 4 legged front seat passenger. If it happens to be a "Buck" it can be especially nasty.
To answer your question about what it takes to set off the air bags, well, that's a good question.
I've seen some cars with devastating front end damage, and the air bags were still intact. Then I've seen a few cars that had only slight damage, and the air bags went off and caused alot more.
I guess it's all depends upon exactly what area on the front of the car receives the brunt of the impact. If the airbag sensors aren't disturbed, the bags do not deploy.
I'm sure someone with a little more body repair background than I have can explain it alot better.
Just be glad yours didn't go off.