Children thrive when they’re in a loving, secure environment so, as much as you can, tell them what is happening in an age-appropriate way.
Be honest with them but remember they don’t need to know everything about why you and your partner broke up. Some conversations are for adult ears only.
What they do need is lots of open communication. They need to know that you’re there to support them, to listen to them and to ease their worries and concerns.
Your lives are all changing but, if you can, try to minimise the practical changes. Try to keep to their usual routines as much as possible for bedtime, school and activities.