Trying to run away would definately be a mistake, even if you did not have the child with you. Even if they were not displaying weapons, one or another might produce one at some moment.
In this particular scenario I would remain in your "corner". Instruct the child to stay put, and reassure him or her as far as possible. At 50 feet, four people armed, acting in the way you describe with impact weapons and knives, are already too close.
A low ready would be in order with a loud and clear command to stop. I might repeat this once if they continued to advance slowly. If this was ignored a presentation would be next with the sights on the closest target. At about 30 feet the closest armed threat would be told, "Stop, or you are first". And I would not bluff.
If none of the subjects displayed weapons I would do exactly the same. Four average males are certainly capable of beating someone to death, and you can not wait until the beating starts to find out if that might be the case.