Our school doesn't do a formal graduation ceremony, they throw a big party for the class. This year, they went bowling. They also do everything you have mentioned, (showing the video with baby pictures, legacy gift to the school, etc.) but in addition, they order shirts that list all of the kids names on the back and the school name/mascot on the front. The kids love them.
I'm sure it's not cheap, but I think if you look around, you may be able to get them at a pretty reasonable price. They even had larger sizes made for all of the teachers, including the music/pe/art/spanish teachers.
Good luck - you've taken on a pretty big project!