I would try to see is there any other options first, if not then I would definitely use lethal force without hesitation and mercy.
Hesitation, mercy and warning shots too usually works in movies, in real life it can be problem, so forget it.
If I am in position to win, I think I would not hesitate there, if I am definitely outnumbered in that combination (and without way out), is it possible to stay hidden? Maybe I would approach it different, try to convince them that they are safe, or that they are outnumbered, confuse them then take them.
There are many variables there, how deep is SHTF (who are they most likely) is my location my home actually etc.