Family share (kids account iCloud ) issues

My kids have been using my AppleID account and it’s difficult as they have access to iMessages and all other apps

I finally created their own Apple ID account and added them under family share.

When I sign out of my apple id and use theirs to log in it’s working but. iMessage is still showing all my message etc.

How can I make sure that they no longer have access to my iMessage and apps. Do I need to factory reset?