For my daughter's 13th birthday, I surprised her with a mall scavenger hunt. I told her to choose 2 friends (figuring if it got too big, it might get difficult for them to coordinate and communicate). I picked the girls up and took them to the mall. We ate at the food court and then I told them they were going to participate in a timed scavenger hunt. I had a grid with 12 categories with four levels of points. The first level was something simple and didn't involve them having to get anyone else involved. The fourth level required them to actually get someone to take their picture OR be in the picture with them. Some categories I selected included: make up, shoes, video, mattress, etc. An example was:  Food 1 pt A picture of someone eating food 2 pt A picture of two of you next to someone eating food 3 pt A picture of all of you next to someone eating food 4 pt A picture of someone sharing food with each of you They had to take a picture to prove it. I gave them strict mall etiquette and safety instructions, a cell phone, a digital camera, and a time limit.  When they returned, we went through all the photos and counted up the points. I, then, let them know that each point was worth $0.25 for each of them that they got to go spend in the mall (so it was a maximum of $12 a girl). After it was over I made the photos into a memory book for my daughter. She loved it...and now I am having to put something similar together for my 12 yr old's next birthday.  I have the spreadsheet of the scavenger hunt that I'd be glad to share, if you wanted to see it.