Lady Macbeth or Desdemona?

i have a slight problem here. for school in cl we are doing Shakespeare and i was chosen to be Lady Macbeth. we just finished setting up the clroom today and didn't get to act it out. i am going on my band trip tomorrow and cant be in it, but my teacher said i could be Desdemona in Othello. should i stay at school and play Lady Macbeth, or reminder her that she said i can be Desdemona next week? i also feel kind of bad cuz some of the other girls want to be Desdemona. also, my band trip is just going to halifax, playing mini golf, eating lunch, and a 2 hour session at long and mcquade. anybody have any advice?