No, no, NO! The warm-ish mac&cheese has been at a temperature in the "danger zone" for many hours. The danger zone is a temperature at which bacteria flourish. No amount of nuking it is going to kill the bacteria. You are more likely to kill your pot-luck friends. Do not under any circumstances serve this to people. Now you know better.
If you thoroughly reheat it, it should be fine. I've eaten non meat stuff I've left out over night, after thoroughly reheating it and I've never had a problem.
this made me lol
Have a bucket near by? get plenty of toilet paper in