I would ask for a copy of the tracker record they have, as they could see the cars API heading data or as they say on a more basic level only see what you can see if the Fabia as an app, you can see where the car is when parked, no matter how far away. But you cannot see it while driving.
When you walk ro your fathers to get the car and drive back to collect your grandad do you park the car and go inside to collect you grandad, as this would trigger two parked events in engine off state. If on the other hand you drive round to your grandads and you wait in the car with the engine running whil’st the engine remains running, because you can’t park, then the second parked event will not trigger! In this case you will need think carefully, how you will need to explain in full detail exactly what happens, without leavng yourself open and is best done in writing imo.
When you ordered the car did you make them aware the car will be parked outside your fathers (if you forgot, I would equally explain why to them)?
On the otherhand, if you are fiddling the system, they will eventually catch up with you.
Best of luck!