This is a document I made awhile back to keep track of who was attending Activity Days. As you can see, in the top half you can fill out the names of the girls in your group; on the bottom half you can write the names of any visitors, and the name of the girl that they came with.
Hope that makes sense. I think it's pretty easy to figure out; if not, let me know.
Oh, as you can see, this is only for the latter part of the year.