Is this something I should come clean on?

The incident in question is well outside the SF-86 reporting window for mental health counseling, so you're okay there. You will have the opportunity to remember or clarify any information you forgot to include on the SF-86 during your personal interview. Of course, this incident was not within the last ten years, so you needn't mention it to the interviewer at all. (Unless they ask!) As for your parents, they should remember when this occurred, right? If they don't, just remind them.