For parents and others talking with children, these resources will be of great help.
The American Psychological Association: Information on Pandemics has a wide range of information to help understand the current situation.
For more specific mental health concerns:
The National Association of School Psychologists: Parent Resources has a great deal for parents who may not know how to talk about the pandemic.
The Youngminds website is very useful for ways of approaching difficult topics, such as how to deal with the implications of the Corvid-19 outbreak.
NHS Berkshire West have put together some reliable and free sources of information and advice to help you and your family to cope under lockdown.
For help in talking directly with children these might be of some help: