Loula, I don't have any advice at the moment, but what a great idea!!  We are having a 50th birthday party for my older brother on the 23rd, that was supposed to be a surprise but we had to let the cat out of the bag due to visitation schedules for his kids being changed when his ex decided to move four hours away!  I am scanning pictures onto the computer to put together a powerpoint presentation.

Your scavenger hunt sounds like sooo much fun  - hope you get everything put together!