I fight these all the time. If he was pacing, it USUALLY doesn’t hold up unless the LEO brings in the last time his speedo was calibrated...they’re not around here usually so thats hard to come up with.
Unless your grandson was under a chopper that was timing him between the lines drawn on the interstate this is easily a winnable ticket. Also depends on how fast he was going. Speeding through a neighborhood will bring zero sympathy from a judge or magistrate, doing 11 over on the interstate is a different story.
If its its worth it to you, pay an attorney $150 to get rid of it. “Lessons” aren’t learned from hiking up insurance premiums and things of that sort. Whether or not your grandson learns a lesson has zero do do with paying the ticket imo, it has to do with how he is punished, if at all. Thats your business, you asked about a ticket not how to be a grandparent.