As for wanting to confess, five years has passed and it is doubtful the elders will do anything about it. In fact, it will probably be deemed "uncleaness" and they will counsel and console her. When you are approached, you might want to simply state that you felt distressed about it as well and looked up information on it in the Index. Because it was not "porneia" you confessed in prayer and vowed to never do it again.
Elders like when people look things up...it makes them believe that people are being responsible for their spirituality. Telling them that what you read didn't move you to speak to them because it wasn't "serious" helps them to feel special because now they have the opportunity to counsel you and "play the part" of the spiritual doctor.
Ultimately, you have to make your own decision, an option might be to tell your wife that you have decided to contact brother "old and caring elder that gets emotional and treats everyone likes his kids" so that you can clear the air.
Good luck,
SOP