Even if your children have avoided any news of the situation in Ukraine up to now, it is highly likely they will have heard about it in school from friends or in age-appropriate classroom discussions, so the resources above may be really useful if your child is anxious about what they are seeing/hearing.
For the grown-ups, a really useful Twitter thread from Ros Atkins (of the BBC’s Outside Source) which contains some short videos to help understand a number of aspects of what is happening now and what has led up to the current situation. Hopefully if we are better informed, it will increase our ability to support the children in processing what is happening.
https://twitter.com/BBCRosAtkins/status/1497499805198819333