I recently set up a scavenger hunt for my fiancée and created a book just like the one from Up for her with clues and photos of us and all kinds of stuff. It happened in Chicago, but it could easily be done at one the parks, preferably MK. I would have definitely done it there if I had the chance too. It helps to have other people in on it too so you don't have to see her til it's time to pop the question