How to tell old participants from new registrants

Hello! I was able to mark new Registrants for 2017 with a “Welcome” Badge so that I can make reports on how many new participants we have. How can I configure a way to catch past returning participants other than by their first badge for reading? I would like to avoid having to do this manually, if possible. Most children come in to the library to record time and get prizes.
We will need to update their information instead of register them. Is there a way to trigger a “Welcome Back” badge when we update?