Alyson Jones, a well-respected West Vancouver family and child counsellor, collaborative coach, parenting coordinator, parent educator and author, has published an article in the Huffington Post about how parents can tell their children that they're separating. Most parents find telling their kids about their separation to be extraordinarily challenging. In fact, noted clinical psychologist Joan Kelly has found that a ridiculously small number of children, less than 20% if I recall, are told anything about what's going on between their parents and that this can have negative short- and long-term consequences for children's wellbeing.
I won't spoil Alyson's helpful article you really should read it but here's a short digest of her main points:
1. Prepare for the talk by meeting with a mental health coach expert in parenting issues.
2. Tell the children together. Take the talk seriously; don't be too casual in your approach.
3. Although you shouldn't be afraid of your children's emotional reaction, you can't get carried away by your own; be strong.
4. Tell the children that you both love them and that this will never change.
5. Tell the children what will be different in their lives and what won't.
Gary Neuman's book, Helping Your Kids Cope with Divorce the Sandcastles Way, is another helpful resource on this subject.