My daughter and my nephew are 9 months apart (he is 18 months, she is 9), but she is a giant and they are the same size. They got a chance to play this weekend while my nephew was visiting with my parents and they were a blast to watch. My daughter was honestly kind of the bully in the situation. :)
I've never used mini clothes pins on a layout, but a banner seemed to make the most sense to me, particularly since I had those awesome BG wooden banners.