I saw a paintstik demo this weekend. They are really chunky and would be hard to get a nice signature. If you found a small stencil, people could stencil their names on with a pastel paintstiks.
I work at Hobby Lobby - let me see what might be available when I go into work this evening! My first thought was pigma pens but I do not think they have a white.
Another option would have people sign their names and you go over them and use them as the quilting for the chalkboard. Could even add the teacher lines that they used to draw when they taught penmanship.