Learned Experience and Guidance

Working at Six Flags has been an eye-opening experience. Manipulating live sound as opposed to the pre-recorded sound I'm used to at Drake is very different. I've gotten better at getting the best sound with the least likely amount of damage to the equipment (always a good thing), and because I'm run one show in particular every day I work, I'm learning not just what songs the cast gets excited about (therefore increasing the chance to overload the mics), but also within the songs, which parts are higher/ louder, and therefore also more likely to cause damage.

An interesting thing I've also learned- the train's whistle as it goes by sounds a lot like feedback during some songs... This has caused me panic more than once, although now that I'm getting used to it, it's getting better and my blood pressure is staying at a nice, healthy rate.. :D

But here's where I could use some help. According to the head of our department, we should be doing a mic check before every show. I agree with this; the majority of the cast does not. It doesn't matter how I phrase the request, or if I give them a few minutes warning or ask that it be done immediately, they always have the same negative reaction. I don't like feeling like the bad person, but at the same time, it takes less than five minutes. All the cast does backstage is mess around and play games between shows, so it's not like I'm asking them to come back from break early or something else that Six Flags could get into legal trouble with or something else along those lines.
So today I tried something new: I didn't remind them of the check. What happened? Before our first show, they had six (6!) minutes to get their mics on, do the check, and get backstage so I could open house. Before our second show, I gave them a fifteen minute warning before I opened house (this is usually when we did the mic check). One girl didn't quite hear and came onstage with her mic on. As I was about to start the check, she asked if that's what we were doing. I informed her that I was simply giving them a house- opening warning, and would be happy to do a mic check if she wanted. She declined and went backstage once more.
As many of you probably know, I usually fly by the seat of my pants. During shows, however, doing this makes me extremely uncomfortable. I worry constantly to the point of making myself nauseas. So obviously I should be doing a mic check for my own sanity as much as because that's what our head of department wants. Here's where I need your help: how do I do this? Above is what I've tried, and it doesn't work (at least, not in any positive manner). So I'm asking for suggestions for some type of middle ground. Yes, they're being whiny little whatevers, but I can't go off on them (as much as I'd like to) because that won't solve anything... So please-- help?