Pitbull, goat and cabbage

If your sword is short, stretch it one step forward.
(A French proverb

The departure was postponed for another hour and we killed time by puzzling each other puzzles: old and new, children and adults, with puzzles and just mathematical puzzles.
Operator Maxim said:

- Let me tell you a real mystery, real, in the sense of my life. My mom solved it in just a minute, maybe even in forty seconds.
You are here, not counting me, four adults and smart people, let’s check – in how long will you find the right answer?
So it is: the beginning of the nineties. The whole country was divided into bandits and victims. But what to tell you? You are older than me, and you should remember that.
Thin thirty-year-old woman, height: 1 meter 60 cm – my mother and two young children: ten-year-old me and my three-year-old sister. We went for a walk to the river – sandwiches to eat, to play badminton, and sandstorms to catch. Somewhere in mid-September, swimming has long been cold, but you can still fall on the blanket. Our river is deep, but rather narrow, about ten or fifteen meters wide in that place.
My mother and I started playing badminton, and on the other side of the river was a company of bandits on two nine. Leather jackets, shuffles, music, girls, all things and they had a fierce dog – like a staff, or a pitbull. A dog, of course, without a leash and a stitch. And once this dog immediately hated our badminton, whispering, voicing, teeth crawling. Only the river saved me.
The bandits began to scream at my mother: "Who, tram-param, the dog you irritate your tram-param with badminton tram-pump from here, or you will be tram-param.
We, of course, were upset, but there is nothing to do, even on different shores, and it is better not to connect with the bandits. We started to fold the blanket and here we hear on the other side - the "bulls", looked around, and this pitbull did not stand, jumped into the water and sailed in our direction to eat everyone.
The bandits themselves were afraid of the consequences, but he does not react, and the owners do not rush into the cold water behind the pitbull, there are no fools. We started shouting, “Tram-param from there, as long as there is time, maybe you will have time to get to the forest!”

Here is the task: you four are my mothers, to you and your children a torpedo-killer flies, seconds after forty, it will already be here, and three hundred meters to the forest.
Decide, the time has passed.

Someone of us proposed to run away, so two of the three are guaranteed to survive, someone to send the children forward and run behind them, so that the children can be saved, someone, screaming loudly, scratching their teeth and standing on the four.
I suggested wrapping the blanket on the hand to take the first bite on it, and there it will be visible.
When the ideas exhausted, Maxim paused and said:

Are there no options anymore? To be honest, it’s been twenty-five years since then, but I’m still wondering – and how did my mom get the right answer in forty seconds? Apparently, when your children are in deadly danger, the brains from the daylight suddenly switch to complete illumination and themselves issue the only correct decision.
My sister and I even thought that my mother was crazy. She took a badminton racket and, as she was in jeans, entered the belt into the water, right in front of the floating death.
I said, “Mom, what are you? “Let’s run, Mom!”
When the pitbull floated to his mother, she carefully plunged his head with a rocket. He stood a little under the water, turned around and went out to the shore.
The gangs on the other side were running, shouting, even kneeling into the water, but they did not decide to swim, whether they were afraid of the cold water, or my mom's rocket.
The sister asked for a long time:
Did you drown a dog?
What are you, daughter? This dog loves to dive and can even live underwater.