Money Tree

I need help fast!! I am holding a 50th wedding anniversary for my grandparents and I need a few ideas. The party is more of an open house and will be held during the afternoon. It is going to be very informal but opefully elegant at the same time. What I need is an idea on how to handle monetary gifts, I was trying to think of an idea for a money tree or something similar but I need help. Also I need an idea for a party favor to give to our guest. I would appreciate any kind of help I can get. Thanks