In general, shuls tend to rely on the principle that these communal issues are considered tzorchei rabim (needs of the community) (Tzitz Eliezer 4:4, ד”ה אך ירשה), and they can use direct amirah for a de’orayta when necessary (Mishnah Berurah 276:25). Given that, besha’at hatzorekh, and especially considering the potential danger posed by hot plates, this approach can be justified. However, with a little advanced planning, you shouldn’t need to rely on this leniency.

Turning off the lights is not just about saving money, and taking out the trash is not merely for convenience. These actions are also to address concerns like unpleasant odors.

It should also be noted that everything you’ve described is derabanan, since even turning off the lights and hot plates is not de’orayta because there is no Gachelet Shel Matechet involved (see Shulchan Arukh HaRav OC, Kuntres Acharon 495:2). If this is the case, then you have a situation of shevut d’shvut bimakom tzorchei rabim (a double rabbinic prohibition in the context of communal needs). However, based on the degree of need regarding the lights and trash, this might not rise to the level of tzorchei rabim.

Even if it is hard to fully characterize it as tzorchei rabim, nevertheless, given the above considerations of shevut d’shvut and some degree of tzorekh, it would certainly be permissible to inform the non-Jewish person before Shabbat, and it is best if you can be indirect: “The hot plates will need to be unplugged” etc. (Shulchan Arukh OC 307:2, Mishnah Berurah 307:10).

If you didn’t arrange this before Shabbat, your last two options also work by adding another layer of derabanan, although you need to carefully consider the chinukh (educational/habituation) factor when involving a child (Mishnah Berurah 307:76).