Ideas for a high school grad trip?

I am currently seventeen and in my last two months of grade 11.
I am looking to go on a trip with a few friends in the summer after we graduate from grade 12 (which would be in a little over a year). However, we need to sort out the details of this trip now.
I was wondering if anyone had any ideas for a destination?

Additional details:
-The trip must be suitable for a group of 18 and 17 year-olds.
We originally looked into the possibility of a cruise, but most every cruiseline has restrictions stating that their must be an individual at least 21 years of age in our party.
-We are looking to spend no more than around $1500 each. Obviously, the cheaper, the better as we are covering the cost of the trip ourselves.
-We live just outside of Toronto, Ontario.
-We are thinking of going away for about a week.
-Pretty much open to anything!

Thankyou in advance for all your input! :)