Snap chat/ pastor

My kids have snap chat. They're only allowed to have siblings and me and dad and grandma on there. We send funny videos or videos of the animals on the farm out back. Anyways I told my kids they're not allowed anyone else on snap chat. Well, our pastor has been giving them a hard time because he knows they have snap chat and won't add him. He asks them all the time why they won't add him and stuff... advice? Thank