<human>: Can you summarize the given text in a few sentences?

Hey all. I am 5'2" 110lb female, and am trying to figure out which martial art to pursue. First, some background. 

I work in a daycare-like setting at a church two days a week. Myself and another teacher are in charge of 8 babies at a time for six hours. We have a half door as the entrance to our room that is always locked. 

One of our parents brought up a concern about lack of security for the kids. True, anyone can enter the facilities, but we will not hand children over to anyone who is not authorized by the parents. 

But it got myself and my boss talking about what we would do if someone came in and tried to hurt either myself, my coteacher, or one of my charges. What if they had a gun? What if they were twice, three times my size? 

Obviously I would try to get between any intruder and my kids, try to talk them down, but if worst came to worst, I want to be able to protect them better than just taking a bullet.
<bot>: what martial art do you suggest for a 5'2" 110lb girl looking to protect children and herself from someone larger than her, possibly with a gun?