Internet Matters is a UK site specifically for parents to use regarding detailed, up to date information about how to keep children safe online.
Common Sense media is a US site which is excellent for parents to see further information on the apps children are using and the games they are playing.
The CEOP (Child Exploitation and Online Protection service) website provides information and resources for parents and carers on keeping your child safer online
The NSPCC website provides advice and guides to help parents learn about staying safe online as a family.
https://www.nspcc.org.uk/preventing-abuse/keeping-children-safe/online-safety/