Write to all 25 classmates, individually. I mean, write a different thing to each classmate in order to uphold their goodwill toward you. It's more sensitive and they'll basically still like you. They should be letters. Write something personally to each student, it's the right thing to do. Emails would be kind of insensitive. Also insensitive would be writing the same thing to each student. It's like recieving a Christmas letter from your boss where every employee's is exactly the same, telling you the boss is putting forth little effort. Or something. I have a question. In the scenario, why must YOU tell everyone? Why is it your responsibility? Are you the class representative or class president or something?
I asked my instructor and she said I am the one who planned the trip lol, but I have to write one letter of 350 words,about the things that i explained
oh so you have to write 1 letter to all 25 people okay. just explain that it's a really unfortunate situation and it's not theirs nor your fault. say that you didn't have any control over that happening and that you wish this would not have turned out the way it did. encourage them to join you to fundraise the same or another trip, and make some gentle jokes, like somthing about making sure to get a different bus company or fly there instead or something.
Frankly, if you planned it, and I were the students, I would hold you accountable for the loss. And you want my goodwill? Ha. Fat chance.