I appreciate your respectful concern. Trigger warnings can be verbal. They can also be informal and come in the form of a spoken content advisory that doesn’t actually use the term “trigger warning”. Looking at the data cited in my piece, that is how TWs most commonly are used. I would advise you do something of that sort before introducing works with potentially triggering content. I am sure there are students who are affected in some way by the suicide in Romeo and Juliet, or the violence in Lord of the Flies, or etc.
It would be responsible and also respectful of their autonomy, I think, to just…talk about these things, very openly, before delving into the book in class. To beat a horse that has already been pummeled to death, providing a heads-up about upsetting content should not lead to the removal or censorship of any content. That said: I totally understand your concern about overreacting parents. I had a lot of LGBT+ and sex-education programming cancelled in high school because of a few pushy “concerned” parents. I know it’s a really tricky, really scary thing for K-12 educators to deal with. It’s a very legitimate fear.
I also am sure you’re great at talking with students on a candid, respectful level about the work they read in class. So I think you could/should handle this the same way you might handle the use of the n-word in Huckleberry Finn, or the way you might handle any sexism or homophobia in other classic works. Acknowledge it, warn students about it, ask them to chime in with questions or reflections, use the warning as a moment to teach about the historical context or about just being sensitive to these things, and keep any TW’s off paperwork unless specifically requested by students, because you know what a minefield it can be.
That’s my read of the situation, but of course you’re the expert on what will work for your class and your population of students. I do think there is a way to provide this accommodation without coming under fire, and that doing so is the responsible choice, as far as students with trauma histories and triggers are concerned.