Airtag beeping even when shared

I have given AirTags to my kids when they travel to France to visit their grandparents. They don’t have a phone so the AirTags are registered to my phone.

I successfully shared the AirTags with their grandparents. After 3 days of being at their grandparents the AirTags are beeping - I am not there with my kids.

Why are they beeping when they have been shared with their grandparents? Is there a way to stop the beeping without marking them lost?

The AirTags are shared with the grandparents hence it should not be a stalking prevention situation with a beeping AirTag.

thanks for the help in finding a solution.