There are many things to help children deal with separation and they can vary depending on the child’s age. But there are some things that all children, regardless of age, need.
Protection from parental conflict.
A secure emotional base.
Help to solve their problems.
Firm and reasonable limits to be safely independent.
Routines that help them feel in control.
Protection from trauma.
Protection from parental stress about ongoing unresolved issues with ex-partners.
While not everything above is within your control, it is really important to think about what you can do to support these needs.
Regardless of age, children will most likely be affected emotionally by the separation and will need understanding and support. They need to know that the separation is not their fault and their job is not to reunite their parents.
One of the most important needs children have is to let them know they are loved, and that this will always be the case.