Ethical Decision

If its just a part-time job your talking about then I'm sure the people who have been laid off will have little trouble finding other work, if they are good enough. It's not the end of the world if they get fired, same applies to you. If you do get fired I'm positive someone like you would have little trouble finding another job, maybe not quite the same, but a job anyway.

I've managed to have fairly good working relationships with my bosses. I've never been fired (yet), survived owner change overs in small businesses, with the old boss putting in a bad word for me (bastard) who I thought I had done well for.

A boss is there to make sure his staff do their job. I don't want to give a shitty definition, but a boss also has to support his/her workers because he/she relies on them to make them look good. I hate work politics, luckily I don't have to worry about it too much in my current job because I'm a contractor (waiter/bar tender) so I just come in, do my job and leave. No problems.

I wouldn't want to be in your position, but as soon as you say something to the potential firees, then they would make some noise (I assume their normal and would enquire to the boss about their position, thereby giving you away as untrustworthy). It sucks, but if you don't want to know about it then tell him so, otherwise he will keep putting you in the same position, and I'm sure you will keep thinking about it. I assume its playing on you mind enough because you have put it on this forum.

You can break it down quite easily;
-do nothing,
-tell your boss not to tell you anything,
-tell your work mates, or
-quit.

Just think of how you would feel if you were told, out of the blue, that you were fired. It would create a working environment that I wouldn't want to work in, with the feeling of being fired at any moment.
-quit.