We did the same thing for my son's graduation last month!! His trip was a surprise.
At his graduation dinner, I gave him a booklet with many pages:
It went like this, one page at a time:
You've Graduated High School
What Are You Going To Do.....
You will Mow The Grass
You will Do The Dishes
You will Do Laundry
You will Clean Your Room
You will Get a Job
You will Play Baseball
You will Finish Your Eagle
You will Go to College
But First.......
You're Going To Disney World!!!!!
Then we handed him his Voucher for his Park Hopper and Airline Ticket.
He was speechless. It took him a few minutes to realize that we were leaving the next morning. He kept saying, but what about work, what about ball games. We had already arranged everything with his boss, his coaches, and his girlfriend. It worked out great!
Carol