Yes for my sins my backround is all sales!! The thing is they have asked you to put this together yourself to show that you have the ability and presentation skills in front of an audience - so it would be wrong for us to do it for you - but am happy to give you some things to mull over
One of the acronyms used with Sales is AIDA - this is what you will need for the presentation, it stands for
Attention - get their attention be interesting and confident
Interest - give the benefits of what these holidays/products have done for other school groups - educational- safe - insured - easy admin etc
Desire - this is the bit where you have to make them want what your selling!! Why should they do it? Happy kids - happy parents - maybe its a hgoliday the parents could not afford to take their kids on as a family, so great the school is doing it etc......, this is where you would also use testimonials from other schools that have done this before and what it meant to them.
Action - You now have to ASK for the sale - or TELL them, this is where you close the deal.
Try and think of all the benefits these holidays can offer.