Is there an app for kids to message their family?

My kids got a tablet for Christmas, & I was wondering is there an app that’s safe for kids to message family members? My daughter loves to text her grandma. I’m mainly looking for something where people can’t send her messages that we don’t know.

Kid messenger you set it up through you’re fb

The people she talks to has to have fb though and you add them and can see everything

Stars messenger or just talk kids

Messenger kids. It’s connected to your fb so they don’t need a fb account. You can also see and choose who they can talk to.