how to 'share our location' with my son

how to share 'find my location' with my adult son who has already set up with another 'family'. Iphone says you can't be part of 2 families for sharing

We are elderly and he wants to be aware of when we travel. But we don't need to have access to all his apps as part of his wife and children's family.

Is there a way to share this app?