Would you be happy (rather than surprised) to see a photo of two male models on your invite to this event in the same style? Maybe with their shirts undone to their waist, sharing a kiss, anything that's approximately equivalent?
If not, you might like to consider why that choice of image would be uncomfortable for you and that this particular choice of image might be uncomfortable for others.
If you bite the bullet (well done!), there are further problems. This is an event to launch a high school seniors employment initiative. High school and sexualised imagery don't belong together.